brkrst-2336
DESCRIPTION
IPTRANSCRIPT
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EIGRP Deployment in Modern Networks BRKRST-2336
Donnie Savage
Don Slice
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2013 Cisco and/or its affiliates. All rights reserved. BRKRST-2336 Cisco Public
Why EIGRP?
EIGRP is easy to design and support Faster system design & deployment time
Easier learning curve for support personnel
Lower Operational Costs (OpEx)
Optimized for Enterprise and Commercial Networks Flexible design options
Sub-second convergence since inception
Simple for small networks, yet scalable for very large networks
Excellent Campus and Hub-n-Spoke WAN protocol
Excellent Scalability in DMVPN deployments
Proven Deployment The most widely deployed enterprise routing protocol
Widely available across Cisco platforms suitable for Enterprise & Commercial
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EIGRP Moving into the Future
EIGRP Information Draft published to IETF
Announced at Cisco Live London
Competitive Landscape; Currently there are at least 4 known companies shipping BEIGRP
in Asia and Europe today.
Current talks with major US based vendors
IPv6 is offering a green-field deployment to customers, and customers are looking at "standards based solutions.
Pressure from public/government sectors who have mandates to use Open solutions when available
Removes the "standards" argument now allows customers to use the technology that best fits their needs.
Development of new features and better scaling are in progress
Cisco is committed to continue offering best of breed
2013
Open-EIGRP: draft-savage-eigrp-00
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Feature Overview
IOS-Classic / IOS-XE IOS-XR NX-OS
BFD Yes Roadmap Yes
IP Fast Reroute 3.7 Roadmap Roadmap
Non-Stop Routing 3.9/3.10 Roadmap Roadmap
UCMP Yes Yes No
EIGRP add-path 3.8 Roadmap Roadmap
VRF-Aware EIGRP Yes Yes Yes
EIGRP PE/CE/Extended Community Yes Yes Yes
EIGRP 6PE/6VPE 3.9 Roadmap Roadmap
EIGRP IPv4/IPv6 MIB Yes/3.7 No/No Yes/No
Route Tag Enhancement Yes No Yes
EIGRP Multi-Instance Yes No Yes
EIGRP Prefix Limit Yes Yes Yes
EIGRP Route Authentication Yes Yes Yes
EIGRP HMAC-SHA-256 Authentication Yes No No
EIGRP Wide Metrics Yes Yes Yes
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EIGRP Deployment in Modern Networks
Typical enterprise network is built upon multiple levels of switches deployed in three general layers: access (to include WAN Aggregation), distribution and core
Core: Provides high speed connectivity between aggregation layers - gets traffic from one area of the
network to another.
Distribution: Provides aggregation of traffic flows from multiple Access layers to the Core. Traffic filtering and
packet policies are typically implemented here. The distribution layer should be the blocking point for Queries (more about this later)
Access: Provide connectivity to user attachment points for servers, end stations, storage devices, and other
IP devices. Consider use of EIGRP STUBS (more about this later)
WAN Aggregation: Provides connectivity to the internet and/or remote sites/offices.
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EIGRP Deployment in Modern Networks
Building 1
Distribution
Access
WAN Aggregation
Application Acceleration
VPN
Building 3
Core
Firewall
Internet Servers
Mail Servers
Core
Building 4 Building 2
Data Center
WAN
Internet
Mobile Worker
Remote Office
Branch Router
Regional Office
Regional Router
Application Acceleration
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Address-Family Support
EIGRP Address Family Support for IPv4/IPv6
With the introduction of EIGRP support for Address Families (AFs), EIGRP supports IPv4 and IPv6 under a single router instance
Reduced complexity
Helps enable IPv4 and IPv6 address families to be supported on a single network infrastructure.
Can be phased in, or applied in green fields
EIGRP IPv4 and IPv6 can be run concurrently
Each address family has a separate topology tables
No Fate Sharing
Design deployment techniques are the same for IPv4 and IPv6
Minimal differences mean no lengthy training required
Configuration and Troubleshooting similar
Same Route Types (Internal, External, Summary)
router eigrp ROCKS
address-family ipv4 autonomous-system 1
network 10.0.0.0 255.0.0.0
!
address-family ipv4 vrf cisco autonomous 4453
network 192.168.0.0
!
address-family ipv6 autonomous-system 1
af-interface Ethernet0/0
shutdown
exit-af-interface
!
address-family ipv6 vrf cisco autonomous 6473
af-interface default
no shutdown
exit-af-interface
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Address-Family Support
Named Mode(multi-address family)
Can be phased in, or applied in green fields
Reduced complexity
EIGRP support for IPv6
Link local routing brings a concept of scalable routing
Uses IPv6 transport and uses link-local addresses as source address.
EIGRP IPv4 and IPv6 can be run concurrently
Cisco supports both
Each address family has a separate topology tables
No Fate Sharing
Design deployment techniques are the same for IPv4 and IPv6
Minimal differences mean no lengthy training required
Configuration and Troubleshooting similar
Same Route Types (Internal, External, Summary)
IPv4 IPv6
IPv6 IPv4
IPv4 IPv6 IPv4/IPv6
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Address-Family Support
Behavior of autonomous-system command under VRFs has changed to address common configurations errors.
router eigrp 1
address-family ipv4 vrf RED
autonomous-system 99
network 10.0.0.0
!
router eigrp 1
address-family ipv4 vrf RED autonomous-system 99
network 10.0.0.0
!
router eigrp 1
address-family ipv4 vrf RED autonomous-system 99
autonomous-system 99
network 10.0.0.0
!
router eigrp cl013
address-family ipv4 vrf RED autonomous-system 99
network 10.0.0.0
1 The AS must be defined for the address-
family to "start" processing
2 The AS Can be entered on the address-
family or standalone or both
3 The AS will nvgen wherever it is entered,
if configured both ways it nvgens both
ways
4 The standalone keyword can be removed
if the AS is defined on the address-family
command
5 Once configured on address-family the AS
can only be removed by removing the
address-family
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Address-Family Support Router Support
Classic mode: Configuring router eigrp command with a number.
Named mode: Configuring router eigrp command with the virtual-instance-name
Named mode supports both IPv4 and IPv6, and VRF (virtual routing and forwarding) instances
Named mode allows you to create a single Instance of EIGRP which can be used for all family types
Named mode supports multiple VRFs limited only by available system resources
Named mode does not enable EIGRP for IPV4 routing unless configured
router eigrp [virtual-instance-name | asystem]
[no] shutdown
.
.
.
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Address-Family Support Family Support
Single place for all commands needed to completely define an instance. show run | section router eigrp
Defines what youre routing/distributing common look and feel Provide support for both routing (address-family) and services (service-family) Can be configured for VRFs
Assure subcommands are clear as to their scope Static neighbors, peer-groups, stub, etc, .. neighbor, neighbor remote, etc.
router eigrp [virtual-instance-name]
address-family [vrf ] autonomous-system
exit-address-family
service-family [vrf ] autonomous-system
exit-service-family
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Address-Family Support Interface Support
EIGRP specific interface properties are configuration in the af-interface mode. for example; authentication, timers, and bandwidth control
af-interface default applies to ALL interfaces Not all commands are supported
af-interface applies to ONLY one interface Only eigrp specific commands are available
Properties which are Interface specific, such as delay and bandwidth, are still configured under the interface
router eigrp [virtual-instance-name]
address-family autonomous-system
af-interface default
exit-af-interface
af-interface
exit-af-interface
exit-address-family
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Address-Family Support Topology Support
Topology specific configuration such as; default-metric event-log-size external-client metric config timers config redistribution
Applies to global, or default, routing table
router eigrp [virtual-instance-name]
address-family autonomous-system
topology base
exit-topology
exit-address-family
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Address-Family Support IOS Changes
The auto-summary command is a relic from the days of classful routing. It was enabled by default in pre-release 5 images.
The auto-summarization feature is no longer widely used and 'no auto-summary' has since become the prevailing configuration.
CSCso20666 changed auto-summary behavior to disabled by default.
Because 'no auto-summary' is the factory default setting it will not nvgen -- auto-summary will now only nvgen if it is explicitly enabled.
default nvgen behavior IOS Version (eigrp version)
auto-summary 'auto-summary' : does not nvgen
'no auto-summary' : nvgens
12.2SR(rel2), 12.2SX(rel3), 12.2SG(rel4)
auto-summary 'auto-summary' : nvgens
'no auto-summary' : nvgens
12.2S(rel1), 12.4T(rel1), 12.2SB(rel1)
no auto-summary 'auto-summary' : nvgens
'no auto-summary' : does not nvgen
15.0(rel5), 15.0T(rel5), 12SRE(rel5),
122XNE(rel5) 122XNF(rel5_1),
122(55)SG(rel5_2)
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Address-Family Support IPv6 Support
Internet Protocol Version 6 (IPv6)
EIGRP supports Internet Protocol Version 6 (IPv6)
Same EIGRP protocol, just IPv6 enabled
A familiar Look and Feel means incumbent EIGRP Operational expertise can be leveraged
DUAL performs route computations for IPv6 without modifications
Provides feature parity with most IPv4 Features EIGRP IPv6 MIBS
EIGRP IPv6 NSF/SSO
EIGRP IPv6 VRF-aware
EIGRP IPv6 BFD support
Etc.
ipv6 unicast-routing ! interface TenGig0/0/0/1 ip address 192.168.1.1 255.255.255.0 ipv6 enable ! router eigrp ROCKS !
address-family ipv6 autonomous-system 1 af-interface Ethernet0/0 no shutdown exit-af-interface
! address-family ipv6 vrf cisco autonomous 6473 af-interface default no shutdown exit-af-interface
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ipv6 unicast-routing ! interface Ethernet0/0 ipv6 address 2001:DB8::1/64 ipv6 enable ipv6 eigrp 6473
! interface Ethernet0/1 ipv6 enable ipv6 eigrp 6473
!
ipv6 router eigrp 6473 router-id 10.10.10.1 no shutdown
classic router configuration
Router-ID is require and selected
from highest loopback IPv4 address
from first IPv4 address found on any physical interface.
If no IPv4 address is available, a 32-bit router-id can be configured manually using the router-id command
eigrp named mode configuration
ipv6 unicast-routing ! interface Ethernet0/0 ipv6 address 2001:DB8::1/64 ipv6 enable
! interface Ethernet0/1 ipv6 enable
! router eigrp CSCO address-family ipv6 autonomous-system 6473 router-id 10.10.10.1 af-interface default no shutdown topology base
IPv6 Configuration Primer
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IPv6 Primer
An IPv6 address is an extended 128-bit / 16 bytes address that gives 2128 possible addresses (3.4 x 1038)
IPv6 addresses
64 bits for the subnet ID, 64 bits for the interface ID
Separated into 8 * 16-bit Hexadecimal numbers
Each block is separated by a colon :
:: can replaced leading, trailing or consecutive zeros
:: can only appear once
EIGRP IPv6 Multicast transport
FF02:0:0:0:0:0:0:A or abbreviated to FF02::A
Examples:
2003:0000:130F:0000:0000:087C:876B:140B
2003:0:130F::87C:876B:140B
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A IPv6 Link-local address is used by EIGRP to source Hello packets and establish an adjacency
IPv6 Link-local address is never routed
IPv6 packet forwarding and must be configured first under global configuration
They are auto assigned when you enable the interface
You can configure this manually on an interface
An IPv6 link-local is prefixed by fe80 and has a prefix length of /10
ipv6 address ?
X:X:X:X::X IPv6 link-local address
X:X:X:X::X/ IPv6 prefix
ipv6 unicast
interface Ethernet1/0
ipv6 enable
IPv6 Link-Local Address
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show eigrp address-family ipv6 topology
EIGRP-IPv6 VR(cl013) Topology Table for AS(6473)/ID(1.1.1.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status
P 2040:3333::31:113:0/112 , 1 successors, FD is 281600
via FE80::A8BB:CCFF:FE00:200 (281600/256), Ethernet0/0
P 2040:3333::31:114:0/112, 1 successors, FD is 281600
via FE80::A8BB:CCFF:FE00:200 (281600/256), Ethernet0/0
The Topology show commands are congruent with IPv4
The next-hop is the Neighbors link-local address
EIGRP IPv6 Topology Table
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The information source and next-hop 128-bit address
show eigrp address-family ipv6 topology 2040:3333::31:113:0/112 EIGRP-IPv6 VR(cl013) Topology entry for AS(6473)/ID(1.1.1.1) for 2040:3333::31:113:0/112
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 281600
Routing Descriptor Blocks:
FE80::A8BB:CCFF:FE00:200 (Ethernet0/0), from FE80::A8BB:CCFF:FE00:200, Send flag is 0x0
Composite metric is (281600/256), Route is External
Vector metric:
Minimum bandwidth is 10000 Kbit
Total delay is 1000 microseconds
Reliability is 0/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1
External data:
Originating router is 2.2.2.2
AS number of route is 0
External protocol is Static, external metric is 0
Administrator tag is 0 (0x00000000)
EIGRP IPv6 Topology Table
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interface Ethernet0/0 ipv6 summary-address eigrp 6473 ?
X:X:X:X::X/ IPv6 prefix
router eigrp cl013-ipv6
address-family ipv6 auto 6473 af-interface Ethernet0/0 summary-address ?
X:X:X:X::X/ IPv6 prefix
IPv6 Route Summarization
EIGRP supports summarization of IPv6 Routes
No auto-summary configuration available in IPv6; IPv6 is essentially classless
Manual summarization is supported, as it is with EIGRP IPv4
Summaries can be configured at any point in the network
classic router configuration eigrp named configuration
IPv6 Route Summarization
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debug eigrp ?
fsm EIGRP Dual Finite State Machine events/actions
neighbors EIGRP neighbors
nsf EIGRP Non-Stop Forwarding events/actions
packets EIGRP packets
transmit EIGRP transmission events
debug eigrp packets
EIGRP Packets debugging is on
(UPDATE, REQUEST, QUERY, REPLY, HELLO, IPXSAP, PROBE, ACK, STUB, SIAQUERY, SIAREPLY)
00:52:47: EIGRP: Received HELLO on Ethernet1/0 nbr FE80::A8BB:CCFF:FE00:401
00:52:47: AS 6473, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
EIGRP IPv6 information in existing debugs
IPv6 Event logs and Debugs Supported
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EIGRP IPv6 Event Log
EIGRP IPv6 Specific Debugging
show eigrp address-family ipv6 event
1 06:27:52.115 Change queue emptied, entries: 1
2 06:27:52.115 Metric set: 2040:3333::31:113:0/112 281600
3 06:27:52.115 Update reason, delay: new if 4294967295
4 06:27:52.115 Update sent, RD: 2040:3333::31:113:0/112 4294967295
5 06:27:52.115 Update reason, delay: metric chg 4294967295
6 06:27:52.115 Update sent, RD: 2040:3333::31:113:0/112 4294967295
debug eigrp address-family ipv6 ?
Autonomous System
neighbor EIGRP neighbor debugging
notifications EIGRP event notifications
summary EIGRP summary route processing
IPv6 Event logs and Debugs Supported
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EIGRP IPv6 vs. IPv4
Provides feature parity with IPv4 Features (stubs, scaling, summarization, etc.)
Uses the same Reliable Multicast Transport protocol used by IPv4
2 new TLVs used for both IPv4 and IPv6;
INTERNAL_TYPE (0X0602), EXTERNAL_TYPE (0X0603)
Same Metrics used by IPv6 and IPv4
Similar Concepts
IPv6 Link-local address are used to establish an adjacency (FF02::A (all EIGRP routers); neighbors do not have to share the same global prefix (with exception of static neighbors where traffic is unicasted)
Does not support the default-information command as there is no support in IPv6 for the configuration of default networks other than ::/0
Does not support the auto-summary command
No split-horizon in the default for IPv6 (as IPv6 supports multiple prefixes per interface)
RouterID which must be explicitly configured if no IPv4 address
Differences
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Address-Family Support Security
Hash-based Message Authentication Code (HMAC) EIGRP offers Secure Hash Algorithms SHA2-256 bit Algorithms
The addition of SHA2-256 HMAC authentication to EIGRP packets ensures that your routers only accept routing updates from other routers that know the same pre-shared key.
This prevents someone from purposely or accidentally adding another router to the network and causing a problem.
The SHA2 key is a concatenation of the user-configured shared secret key along with the IPv4/IPv6 address from which this particular packet is sent. This prevents Hello Packet DOS replay attacks with a spoofed source address.
Simpler configuration mode using a common password
Keychain support when additional security is needed
A
B C
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Address-Family Support Security
HMAC SHA2 256bit Authentication
MD5 has been has been cracked and a number of tools exist on various sites to crack MD5 hash
With new peering options in development will allow for multi-hop remote peers, a new method is needed
SHA1 was considered, but SHA-1 is not collision free and can be broken in 2^69 attempts instead of 2^80. While this It was still a nontrivial problem, it could be done so we wanted to consider better options.
SHA2 seems to be the best available and has been shown to be very secure. Block sizes of 512 vs. 256 did not show much difference in security for the additional processing requirements
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Simple configuration using only one password
Additional security can be added with key-chains
router eigrp DC012-md5
address-family ipv4 auto 4453
af-interface default
authentication key-chain DC012-CHAIN
exit-af-interface
af-interface Ethernet0
authentication mode hmac-sha-256 ADMIN
exit-af-interface
af-interface Ethernet1
authentication mode hmac-sha-256 CAMPAS
exit-af-interface
af-interface Ethernet2
authentication mode hmac-sha-256 LAB
authentication key-chain DC012-LAB
exit-af-interface
router eigrp ROCKS
address-family ipv4 auto 4453
af-interface default
authentication mode hmac-sha-256 my-password
exit-af-interface
key chain DC012-CHAIN
key 1
key-string securetraffic
!
router eigrp ROCKS
address-family ipv4 auto 4453
af-interface default
authentication mode hmac-sha-256 my-password
authentication key-chain DC012-CHAIN
exit-af-interface
Interface inheritance can simplify configuration
Address-Family Support Security
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IOS-Classic / IOS-XE IOS-XR NX-OS
EIGRP IPv6 MIB 3.7 No No
Route Tag Enhancement Yes No Yes
EIGRP Multi-Instance Yes No Yes
EIGRP HMAC-SHA-256 Authentication Yes No No
EIGRP Wide Metrics Yes Yes Yes
Stubs/Stub Leaking Yes/Yes No/No Yes/No
Summary/Summary Leaking Yes/Yes Yes/No Yes/No
VRF-Lite Yes Yes Yes
PE/CE Support/Extended Community SoO 3.9/Yes No/No No/No
EIGRP Prefix Limit Yes No No
BFD Yes Planned Roadmap
Performance Routing(PfR) No No No
3rd Party Next Hop/AddPATH Yes No No
Non-Stop Routing(NSR) Yes No No
IPv6 Feature Overview
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Routing Basics
EIGRP only knows prefix and next-hop information
Topology information beyond the next hop is naturally hidden in distance vector protocols
B and C only advertise that they can reach 10.1.1.0/24, not that they are connected to D, which is then connected to 10.1.1.0/24
B
10.1.1.0/24
D I can reach
10.1.1.0/24 I can reach
10.1.1.0/24
I can reach
10.1.1.0/24
I can reach
10.1.1.0/24
A
C
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10.1.3.0/24
10.1.1.0/24
10.1.2.0/24
Routing Basics
Hiding topology information hides information about changes in the topology
C advertises reachability to 10.1.1.0/24 If the F to G link fails, C can still reach 10.1.1.0/24
(although the metric might change)
If B can still use C to reach 10.1.1.0/24, does B need to know about the F to G link failure?
No!
What's the issue if C advertises reachability to 10.1.1.0/24?
When the F to G link fails, C will send an update to B
B may then go active and potentially query its peers
This increases CPU, memory, and convergence time for a path B can not reach
G
D
E F
C can reach
10.1.1.0/24
Hide
topology
here
C
A B
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Routing Basics
When EIGRP goes active, it sends a Query to its peers looking for the lost route.
The Query is bounded by: Local knowledge of an alternate loop-free path not learned
through the peer the query was received from
No local knowledge of the route because of filtering
No local knowledge of the route because of summarization
No peers to query
10.1.1.0/24
Local Knowledge of
an alternate path, So
Reply
Fil
ter
No Knowledge of
Route, So Reply
Su
mm
ary
No Knowledge of
Route, So Reply
No peers,
So Reply
C
D
A
E
F
G
B
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Routing EnhancementsSNMP
Simple Network Management Protocol (SNMP)
EIGRP supports 68 MIB objects in 4 major tables
eigrpRouteSIA and eigrpAuthFailure can trigger SNMP traps
EIGRP Traffic Statistics
AS Number
Number of Hellos, Updates,
Queries, and Replies Sent/Received
EIGRP Topology Data
Destination Net/Mask
Active State, Feasible Successors
Origin Type, Distance
Reported Distance
EIGRP Interface Data
Peer Count
Reliable/Unreliable Queues
Pending Routes
Hello Interval
EIGRP Peer Data
Peer Address, Interface
Hold Time, Up Time
SRTT/RTO
Version
Additional CCO information
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
http://www.cisco.com/go/mibs
ftp://ftp.cisco.com/pub/mibs/oid/
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Routing EnhancementsMANET
Mobile Ad-hoc Network (MANET)
Cisco supports RFC4938bis and Dynamic Cost Routing via using EIGRP
The fundamental requirement for MANET applications is effective integration of routing and radio technologies
Effective routing requires immediate recognition of topology changes, the ability to respond to radio link quality fluctuations, and a means by which routers can receive and act upon feedback from a radio network
New Virtual Multipoint Interface (VMI) and L2L3 API connects Layer 2 RF network with layer 3
Mobile EIGRP
Router Mobile Radio Mobile EIGRP
Router Mobile Radio
PPPoE PPPoE
PPP Sessions
RF
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Routing EnhancementsPfR
Performance Routing (PfR)
Cisco IOS Performance Routing (PfR) supports Route control using EIGRP
Monitors traffic performance for prefixes passively with NetFlow and/or actively using IP SLA probes
Chooses best performing path to a given destination
Delay, MOS
Load Balancing
For prefix, traffic-class and application
Additional CCO information
http://www.cisco.com/go/pfr
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Core
Building 1 Building 2 Building 4
Data Center
WAN
Mobile Worker
Remote Office
Branch Router
Regional Office
Regional Router
WAN Aggregation
Application Acceleration
Application Acceleration
VPN
Core
Firewall
Internet Servers
Mail Servers
Core
Internet
Building 3
Distribution
Access
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Core
Hierarchical Designs 2 Layer
3 Layer
More
Reliability Graceful Restart(GR)
Non-Stop Forwarding(NSF)
Non-Stop Routing(NSR)
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Hierarchy and the Core
Unlimited Network Hierarchy
EIGRP supports unlimited hierarchy though summarization
The depth of the hierarchy doesnt alter the way EIGRP is deployed; there are no hard edges
Core, Distribution, and Access are flexible terms that may, or may not, fit your topology
EIGRP does not force these boundaries
Divide complexity with summarization points
Summarize at every boundary where possible Aggregate reachability information
Aggregate topology information
Aggregate traffic flows
A place to apply traffic policy
Summarize
Distribution
Access
Core
High Degree
of Density
High Degree
of Complexity
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Hierarchical Design
No imposed limit on levels of hierarchy a key design advantage.
No areas or other restrictions on dividing a network
Topology information can be hidden at any hop in the network anyway
In an EIGRP network, the hierarchy is created through summarization, rather than through a protocol defined boundary
Proper addressing is a must to insure you can summarize
With the logical boundary point behind the lower routers, based on the divisional structure, theres no place to summarize
No
summarization
10
.1.0
.0/2
4
10
.1.2
.0/2
4
10
.2.0
.0/2
4
10
.2.2
.0/2
4
10
.1.1
.0/2
4
10
.1.3
.0/2
4
10
.2.1
.0/2
4
10
.2.3
.0/2
4
Sales Marketing
Logistics Engineering
Logical
boundary
points
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Hierarchical Design
The logical network structure no longer follows the corporate departments
We now have a point at which we can summarize routes!
Logical
boundary
point 10.1.0.0/22
10.2.0.0/22
What Happens if We Move the Logical Boundary Point Up One Layer?
10
.1.0
.0/2
4
10
.1.2
.0/2
4
10
.2.0
.0/2
4
10
.2.2
.0/2
4
10
.1.1
.0/2
4
10
.1.3
.0/2
4
10
.2.1
.0/2
4
10
.2.3
.0/2
4
Sales Marketing
Logistics Engineering
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Hierarchical Design
In this case, moving the logical boundary point down one layer can be used to improve summarization
For EIGRP, its just a matter of configuring summaries in the best possible locations
Logical
boundary
point
10
.1.0
.0/2
4
10
.1.2
.0/2
4
10
.1.1
.0/2
4
10
.1.3
.0/2
4
10
.2.1
.0/2
4
10
.2.3
.0/2
4
10
.2.0
.0/2
4
10
.2.2
.0/2
4
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Two Layer Hierarchy
The core gets traffic from one topological area of the network to another
High Speed Switching is the focus
Within the core, avoid Policy within the core
Reachability and topology aggregation (summarization)
Core routers should summarize routing information towards the access/aggregation layers
Routing policy may also be implemented at the core edge
Core
Access
Policy
Summary
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Core
Access
Two Layer Hierarchy
The aggregation layer provides user attachment points
Information hiding Edge routes should be hidden from the core
Summarize routes towards the core
Policy should be placed at the edge of the network Traffic acceptance (based on load and traffic type)
Filtering unwanted traffic
Security policy
Layer 2 and Layer 3 filters apply at the edge
Summarize
Policy
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Customers
Two Layer Hierarchy
ISP networks are often modeled on a two layer hierarchy as well
The core is often mesh or a set of rings, with each POP modeled as a ring or a two layer hierarchy
Topology information is summarized between the POPs and the network core
Address summarization is generally from the core towards the POPs
Core
POP
POP
POP
POP
POP
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Three Layer Hierarchy
The core gets traffic from one topological area of the network to another
High Speed Switching is the focus
Within the core, avoid Policy within the core
Reachability and topology aggregation (summarization)
Core routers should summarize routing information towards the distribution layers
Deeper hierarchy does not change EIGRPs fundamental design concepts
Core
Distribution
Access
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Three Layer Hierarchy
Address summarization and aggregation occur at the distribution layer
Address Summarization At the distribution layer edge and the core
At the distribution layer edge and the access layer
At both edges of the distribution layer
The distribution layer should be the blocking point for Queries
Provide minimal information toward the core
Provide minimal information toward the access
Access layer routers should be considered for configuration as stubs
Core
Distribution
Access
Tra
ffic
ag
gre
ga
tio
n
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Core
Distribution
Access
Three Layer Hierarchy
The distribution layer is where most of the policy in a three layer network should reside
Traffic Engineering Directing traffic into the best core entry point
Access layer failover
Traffic filters
Should take all the policy load off the network core
Routing Policy Routes accepted from the access layer
Routes will be passed from the core into the access layer
Filtering unwanted traffic at Layer 2 and Layer 3
Security policy
Policy
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Three Layer Hierarchy
Summarization should be avoided between distribution layer routers!
This can cause a lot of odd and hard to troubleshoot problems within the network
Focus summarization and policy up and down the layers, rather than along the layers
No s
um
marization! Core
Distribution
Access
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1000 routes
1000 routes
1000 routes
1000 routes
4000+100 routes
400+100 routes
Impact of Hierarchy to Core
Assessing the Impact
1000 routes each failing once/month means 4100/30 = 136.7 state changes per day in the core of this network
Summarizing each 1000 route zone into 100 routes reduces the core to 500, rather than 4100 routes
Summarization hides individual route changes, so we only see the 100 core routes change: 100/30 = 3.3 state changes per day in the core of this network
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Core
Hierarchical Designs 2 Layer
3 Layer
More
Reliability Graceful Restart(GR)
Non-Stop Forwarding(NSF)
Non-Stop Routing(NSR)
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Graceful Restart (GR) / Nonstop Forwarding (NSF)
Graceful Restart (GR) / Nonstop Forwarding (NSF)
GR/NSF are redundancy mechanisms for intra-chassis route processor failover
Graceful Restart (GR) is a way to rebuild forwarding information in routing protocols when the control plane has recovered from a failure
Nonstop Forwarding (NSF) is a way to continue forwarding packets while the control plane is recovering from a failure
Newly active redundant route processor continues forwarding traffic using synchronized HW forwarding tables
NSF capable routing protocol (e.g.: EIGRP) requests graceful neighbor restart
Routing neighbors reform with no traffic loss NSF and fast hellos/BFD do not go well and should be avoided NSF makes more sense in a singly homed edge devices
Control Data
no reset
Control Data
A
B
51
The fundamental premise of GR/NSF is to route through temporary failures, rather than around them!
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Data Center
Building 1 Building 2 Building 3 Building 4
Core
WAN
Internet
Mobile Worker
Remote Office
Branch Router
Regional Office
Regional Router
WAN Aggregation
Application Acceleration
Application Acceleration
VPN Firewall
Internet Servers
Mail Servers
Core Data Center
Distribution
Access
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Data Center
Fast(er) Convergence Detection
Repair
IP FRR
Redundancy Redundant Links
Controlling Redundancy
Full Mesh
High Speed Links Load Sharing
Wide Metrics
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Data Center
Data Centers are at the core of your business activity
Video, voice or other rich media traffic is placing ever-increasing demands on the physical layer
The Core can be used as the data center core. Consider the following items when determining the right core solution:
10GigE densityWill there be enough 10GigE ports on the core switch pair to support both the campus distribution as well as the data center aggregation modules?
Administrative domains and policiesSeparate cores help to isolate campus distribution layers from data center aggregation layers in terms of troubleshooting, administration, and policies (QoS, ACLs, troubleshooting, and maintenance).
Future anticipationThe impact that can result from implementing a separate data center core layer at a later date might make it worthwhile to install it at the beginning.
A robust infrastructure is needed to handle these demands
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Fast(er) Network Convergence
EIGRP Fast Convergence EIGRP support for FAST Convergence already part of the standard
Customers have been using EIGRP to achieve sub-second convergence for years
Bad or no network design leads to bad or no Convergence
Proper network design is a must Design to use address summarization to limit query scope
Design to use link redundancy properly
Design to provide at least one feasible successor
We can sort typical convergence times: EIGRP with a feasible successor
Link state protocols
EIGRP without a feasible successor
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Convergence Comparative Data
EIGRP with feasible successors
IS-IS with tuned timers
OSPF with tuned timers
EIGRP without feasible successors
OSPF with default timers
IS-IS with default timers
0
7000
6000
5000
4000
3000
2000
1000
1000
2000
3000
40
00
5000
Route
Generator
A
B C
D
Routes
Mil
lis
ec
on
ds
IPv4 IGP Convergence Data We can sort typical convergence times into three groups
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Fast(er) Network Convergence
For paths with feasible successors convergence time is in the milliseconds The existence of feasible successors is dependent on the
network design
For paths without feasible successors, convergence time is dependent on the number of routers that have to handle and reply to the query Queries are blocked one hop beyond aggregation and route filters so SUMMARIZE
Query range is dependent on network design so SUMMARIZE
Good design is the key to fast convergence in an EIGRP network
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Improving Convergence Detection
EIGRP Aggressive Timers (Fast Hellos) EIGRP supports aggressive timers to decrease link failure detection
Aggressive Timers does not provide sub-second failure detection
Timers can be tuned to a minimum of 1 second
Interface dampening is recommended with fast hello timers
Additional information There are reasons for not recommending this and also for us not offering such low values; for example, depending on the number of interfaces, 1 sec rates can become CPU intensive and lead to spikes in processing/memory requirements
interface GigabitEthernet1/1
dampening
!
router eigrp ROCKS
address-family ipv6 auto 6473
af-interface default
hello-interval ?
Seconds between hello transmissions
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Improving Convergence Detection
Bidirectional Forwarding Detection (BFD)
Cisco IOS Bidirectional Forwarding Detection (BFD) is a fast Hello at Layer 2.5
BFD exhibits lower overhead than aggressive hellos
BFD is a heartbeat at Layer 2.5, provides sub-second failure detection
BFD can provide reaction time close to 50 milliseconds
EIGRP use BFD facilities which send extremely fast keep-alives between routers
BFD and the Routing Protocol works together, with Routing Protocol as the upper layer protocol
BFD relies on the Routing Protocol to tell it about Neighbors
Notifications occur quickly when changes occur in Layer 2 state
Additional CCO information
http://www.ietf.org/internet-drafts/draft-ietf-bfd-generic-02.txt
http://www.ietf.org/internet-drafts/draft-ietf-bfd-base-05.txt
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Improving Convergence Repair
EIGRP Loop Free Fast Reroute (IP-FRR)
Support for IP Fast Reroute (IP-FRR)
IP-FRR is a mechanism that reduces traffic disruption to 10s of milliseconds in event of link or node failure
Uses existing Feasible Successors, so no additional computational load
Automatically enabled on all interfaces covered by the protocol
Repair paths can be equal or unequal cost (though variance command)
Repair paths are computed for all prefixes though not all prefixes may have a FS (repair path)
But..
It runs at the process level
Does not guarantee time limit
Performance depends on tuning and platform implementation
Primary Path Repair Path
Primary Next-Hop Protecting Node
A B
C
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Enabling EIGRP IP-FRR
IOS implements per-prefix IP-FRR
Per-prefix IP-FRR enabled for all areas unless explicitly specified
IP-FRR automatically enabled on EIGRP interfaces
Repair paths are computed for all prefixes though not all prefixes may have repair paths
router eigrp ROCKS
address-family ipv4 autonomous-system 1
network 10.0.0.0 255.255.255.255
topology base
fast-reroute per-prefix all
. . .
A
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Data Center
Fast(er) Convergence Detection
Repair
IP FRR
Redundancy Redundant Links
Controlling Redundancy
Full Mesh
High Speed Links Load Sharing
Wide Metrics
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Redundancy
The simplest path to increased resiliency is adding redundancy... Adds network resiliency
Can provide optimal routing to resources
Adds additional bandwidth in congested areas of the network
But not so fast!
Adding Links doesnt always add resiliency General EIGRP rule of thumb: There should be no more paths in the topology table than are allowed to be installed in the routing table
The second link also adds moderate complexity, and more information, into the network
(show ip eigrp topology all vs. show ip protocol, look for maximum path)
A
10.1.1.0/24
B
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Redundancy
Adding a third link almost always approaches the point of diminishing returns, and adds much more network complexity
When considering adding more redundancy, always balance the increased resiliency against the added complexity Increased network convergence times
Increased management effort
Increased troubleshooting times
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2.5
0 10000
Se
co
nds
Routes
Feasible successor
Redundancy
The impact of greater levels of redundancy on convergence times can be seen in routing protocol scalability testing
Using EIGRP, with a single backup path, it takes about 1.3 seconds for a router with 10,000 routes to converge when the best path fails
Best path
fails
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Redundancy
The impact of greater levels of redundancy on convergence times can be seen in routing protocol scalability testing
Using EIGRP, with a single backup path, it takes about 1.3 seconds for a router with 10,000 routes to converge when the best path fails
Adding the third path increases convergence time to 2 seconds
Adding the fourth path increases convergence time to 2.25 seconds
2.5
0 10000
Se
co
nds
Routes
Best path
fails
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Redundancy
High availability studies also show the impact of adding the third link is not all that great
Adding a second link will increase reliability significantly
Adding a third link approaches the point of diminishing returns
Combined with the impact of slower convergence times, higher management costs, and slower troubleshooting, the total downtime in a network may actually increase with the addition of large amounts of redundancy
99.50
99.60
99.70
99.80
99.90
100.00
1 link 2 links 3 links 4 links
Relia
bili
ty
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Controlling Redundancy
Consider using Layer 2 interface bundling - EtherChannel, MLPPP(Multilink PPP)
Increases redundancy
Increases bandwidth
Reduces Layer 3 complexity
But be aware of issues such as processor utilization due to bundling overhead
troubleshooting complexity, etc. Link bundle
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Full Mesh
Is this sufficient redundancy, or excessive?
There are potentially 64 paths between these two hosts, 26
2 routers == 1 link
3 routers == 3 links
4 routers == 6 links
5 routers == 10 links
6 routers == 15 links
...
adjacencies = nodes(nodes-1)/2
Not just physical links, VPLS also creates this scenario
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Full Mesh
Routes must be advertised between every pair of peers in the mesh so each router has the correct next hop and routing information
Address the links so they can be summarized
Single advertisement at the edge is best
Address the links so the link information can be filtered out at the edge
Summarize
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Full Mesh
Consider High Availability ring topologies, such as SRP, SONET rings, and others as an alternative to full mesh high speed networks in POPs and other enclosed networks
This can provide resiliency against a single failure in the network, and simplify the topology from the perspective of routing dramatically
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Ring Topologies
If the A->C link fails, A must query B to find the alternate path
If the B->C link fails, no queries will be transmitted to converge
The maximum query range is one hop
5
5 5
1 Hop Query
No Query
A B
C
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Ring Topologies
If the A->C link fails A must query B to find the alternate path
B must query D to find the alternate path
The maximum query range is two hops
5 5
5
5 A B
C
D
2 Hop Query
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Ring Topologies
If the A->C link fails A must query B to find the alternate path
B must query E to find the alternate path
E must query D to find the alternate path
The maximum query range is three hops
Typically the network will watershed
Rings are a challenging topology for EIGRP The maximum query range will always be the size of the ring minus one
Average is ring size divided by 2
If at all possible, design in triangles, not rings!
5
5 5
5
5 A B
C
D
3 Hop Query
E
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Data Center
Fast(er) Convergence Detection
Repair
IP FRR
Redundancy Redundant Links
Controlling Redundancy
Full Mesh
High Speed Links Load Sharing
Wide Metrics
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Unequal Cost Load Sharing
All routing protocols can load share over equal cost links
Can you load share across the two available paths between A and D, if they are not equal cost?
Yes, EIGRP is unique in this respect
Variance allows unequal cost paths to be used as long as the paths are loop free
56K 56K
500K 1000K
A
B C
D
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Unequal Cost Load Sharing
Given the metrics for the following paths:
D through C Distance: 560128
Reported Distance: 557568
D through B Distance: 1069568
Reported Distance: 557568
The best path is through C, so C is the successor
The reported distance through B is lower than the best path through C, so this path is loop free
B is the feasible successor (FS) or backup path 56K
2000ms
56K
2000ms
56K
2000ms
1000K
10ms
A
B C
D
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Unequal Cost Load Sharing
Configure variance on router A with a value high enough to include both paths
Variance is a multiplier, so it has to be a number which, when multiplied by the lower metric, is higher than or equal to the highest metric
Any route with a metric less that the variance metric, will be include in the load sharing
A
B C
D
Metric
1069568
Metric
560128
lowest metric * variance metric of other path
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Unequal Cost Load Sharing
Both paths are installed in the routing table
The higher metric is then divided by each lower metric to determine the load share count: 1069568/5601282
From this point, the actual load sharing of traffic is up to the switching engine being used to forward packets
For process switching, each packet forwarded through B will be matched by 2 packets forwarded through C
A
B C
D
Metric
1069568
Metric
560128
router-a(config)#router eigrp 100
router-a(config-rtr)#variance 2
router-a(config-rtr)#end
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EIGRP Classic Metric Formula
With the simplified EIGRP Formula:
The path has a minimum bandwidth of 100,000 kbps (from R4)
The path though the Ten Gigabit Bundle has a total delay of 120 microseconds
But so does the path through the Gigabit Ethernet!
80
metric =107
min bandwidth( )+ delays
*256
Router1#show eigrp addr ipv4 topology 10.1.1.0/24
IP-EIGRP (AS 1): Topology entry for 10.1.1.0/24
State is Passive, Query origin flag is 1, 2 Successor(s), FD is 28672
Routing Descriptor Blocks:
10.4.4.2 (TenGigabitEthernet2/0), from 10.4.4.2, Send flag is 0x0
Composite metric is (28672/28416), Route is Internal
Vector metric:
Minimum bandwidth is 100000 Kbit
Total delay is 120 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 2
10.5.5.3 (GigabitEthernet3/0), from 10.5.5.3, Send flag is 0x0
Composite metric is (28672/28416), Route is Internal
Vector metric:
Minimum bandwidth is 100000 Kbit
Total delay is 120 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 2
B: 10,000,000
D: 10
B: 10,000,000
D: 10
B: 1,000,000
D: 10 B: 1,000,000
D: 10
10.1.1.0/24
B: 100,000
D: 100
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Computing Classic Metrics
EIGRPs calculated metric is called the composite metric
Its computed from individual metrics called vector metrics - minimum bandwidth, total delay, load, reliability
Interface metrics are converted before use bandwidth (in kilobits per second): 107 / Interface bandwidth
delay (in 10s of microseconds): interface delay / 10ms
load, reliability: converted to range of 0-255
Constants (K1 through K5) are used to control the computation Default K values are: K1 == K3 == 1 and K2 == K4 == K5 == 0
When K5 is equal to 0 then [K5/( K4 + reliability)] is defined to be 1
81
metric = [(K1 bandwidth +
K2 bandwidth + (K3 Delay))
K5 ] 256
256 Load K4 + Reliability
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( )256*
min
107
+delays
bandwidth
Classic and Wide Metrics
Router A advertises 1.1.1.0/24 to B Bandwidth is set to 1000
Delay is set to 100
Router B Compares current bandwidth to bandwidth of link to A; sets bandwidth to 100
Adds delay along link to A, for a total of 1100
Router C Compares current bandwidth to bandwidth of link to B; sets bandwidth to 56
Adds delay along link to B, for a total of 3100
82
Computing Metrics
1.1.1.0/24
BW: 1000
Delay: 100
BW: 100
Delay: 1100
BW: 56
Delay: 3100 Minimum
Added Together
BW: 100
Delay: 1000
BW: 56
Delay: 2000
A
B
C
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( )256*
min
107
+delays
bandwidth
Computing Classic Metrics
Router C uses the formula to compute a composite metric - This isnt what the router computes,
thoughwhy?
- The router drops the remainder after the first step!
Why the 256?
EIGRP uses a 32-bit metric space
IGRP used a 24-bit metric space
To convert between the two, multiply or divide by 256!
83
?
107
56=178571
(178571+3100)*256 = 46507776
46507885256*310056
107=
+
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latency = delay*106OR
1013
bandwidth
throughput =6.5536*1011
bandwidth
metric = min throughput( )+ latency
Wide Metric Support: New Formula
With the Existing EIGRP Formula:
Wide Metrics enables us to; Configure delay values in pico-seconds
Pass raw delay/bandwidth values between peers
Composite metric is computed correctly for high-speed interfaces
RIB Metric still in 32bit form
Router# show eigrp address-family ipv4 topology
EIGRP-IPv4 VR(WideMetric) Topology Entry for AS(4453)/ID(3.3.3.3) for 10.1.1.0/16
State is Passive, Query origin flag is 1, 1 Successor(s), FD is 262144, RIB is 2048
Descriptor Blocks:
10.4.4.2 (TenGigabitEthernet2/0), from 10.4.4.2, Send flag is 0x0
Composite metric is (262144/196608), route is Internal
Vector metric:
Minimum bandwidth is 10000000 Kbit
Total delay is 3000000 picoseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 2
Originating router is 100.1.1.1
B: 10,000,000
D: 10
B: 10,000,000
D: 10
B: 1,000,000
D: 10 B: 1,000,000
D: 10
10.1.1.0/24
B: 100,000
D: 100
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Computing Wide Metrics
EIGRP still uses vector metrics, but they are not scaled, and are processed differently
New vector metrics are derived from values reported by router Throughput derived from interface bandwidth
Latency derived from interface delay
Load derived from interface load
Reliability derived from interface reliability
Extended Metrics derived from router and/or configuration
Constants (K1 through K6) are used to control the computation Default K values are: K1 == K3 == 1 and K2 == K4 == K5 == K6 == 0
[(K1 Throughput + { K2 Throughput
}) + (K3 Latency) + (K6 Ext Metrics) ] K5
256 - Load K4 + Reliability
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Computing Wide Metrics
By default, EIGRP computes throughput using the maximum theoretical throughput
The formula for the conversion for max-throughput value directly from the interface without consideration of congestion-based effects is as follows:
If K2 is used, the effect of congestion, as a measure of load reported by the interface, will be used to simulate the available throughput, by adjusting the maximum throughput according to the formula:
This inversion of bandwidth value results in a larger number (more time), ultimately generating a worse metric.
The inverted value is used only by the local router, the original bandwidth value is send to its neighbors
Max-Throughput = (K1 EIGRP_BANDWIDTH EIGRP_WIDE_SCALE
) Bandwidth
Net-Throughput = [Max-Throughput + ( K2 Max-Throughput
)] 256 - Load
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Classic and Wide Metrics
K3 is used to allow latency-based path selection. Latency and delay are similar terms that refer to the amount of time it takes a bit to be transmitted to an adjacent peer. EIGRP uses one-way based latency values provided either by IOS interfaces or computed as a factor of the links bandwidth
For IOS interfaces that do not exceed 1 gigabit, this value will be derived from the reported interface delay, converted to picoseconds
For IOS interfaces beyond 1 gigabit, IOS does not report delays properly, therefore a computed delay value will be used
Delay = ( Interface Delay EIGRP_DELAY_PICO )
Delay = ( EIGRP_BANDWIDTH EIGRP_DELAY_PICO
) Interface Bandwidth
Latency = (K3 Delay EIGRP_WIDE_SCALE
) EIGRP_DELAY_PICO
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Distribution and Access
Core
Data Center
WAN
Internet
Mobile Worker
Remote Office
Branch Router
Regional Office
Regional Router
WAN Aggregation
Application Acceleration
Application Acceleration
VPN Firewall
Internet Servers
Mail Servers
Core
Building 4 Building 1 Building 2 Building 3
Distribution Distribution
Access
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Distribution and Access
Distribution (aggregation point for access)
Summarization
Summary Metrics
Summary Leak-maps
Filtering
Route Map Support
Route Tag Enhancement
Access (STUB and edge features)
Managing alternate paths
Passive interfaces
Hub and Spoke
Scaling
Enhancements
Leak-maps
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Route Summarization
Route Summarization
EIGRP supports summarization at any point in the network
EIGRP chooses the metric of the lowest cost component route as the summary metric
What happens if the summary metric changes?
If the component the metric was taken from changes, the summary changes as well!
Youre using the summary to hide reachability information, but its passing metric information through
Routers beyond the summary are still working to keep up with the changes
10.1.0.0/23
Metric 10
10.2.0.0/23
Metric 20
10.1.0.0/23
Metric 30
10.2.0.0/23
Metric 20
10
.1.0
.0/2
4
Me
tric
30
10
.1.1
.0/2
4
Me
tric
10
10
.1.0
.0/2
4
Me
tric
30
10
.1.1
.0/2
4
Me
tric
10
A
B C
10
.2.0
.0/2
4
Me
tric
30
10
.2.1
.0/2
4
Me
tric
20
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Route Summarization
Use a loopback interface to force the metric to remain constant
Create a loopback interface within the summary address range with a lower metric than any other component
Generally best to use a /32 for the prefix and use delay to force the metric value
The summary will use the metric of the loopback, which doesnt ever go down
You can sometimes use a route-map to force the summarys metric to always be the same
A static route to null0 on the summarizing router can also be used
A
B
10.1
.0.0
/24
Metr
ic 1
0
10.1
.1.0
/24
Metr
ic 2
0
10.1.0.0/23
Metric 1
loopback 0
ip address 10.1.1.1 255.255.255.255
delay 1
10.1.0.0/23
1
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Summary Metrics
Route Summary Static Metrics
EIGRP summarization efficiency is greatly improved by predefining a summarys metric
Could use a loopback interface or define a static route to null0
Metric will be constant, eliminating update
EIGRP still scans component routes for changes
EIGRP will never withdraw summary
A better solution is to use the summary-metric command which established a constant metric value thereby:
Eliminate the updates
Eliminate re-computing the summary metric when components change
Allows the summary to be withdrawn when all comments are lost
router eigrp ROCKS
address-family ipv4 auto 4453
network 10.0.0.0
af-interface Ethernet0/0
summary-address 10.1.0.0/23
exit-af-interface
topology base
summary-metric 10.1.0.0/23 10000 1 255 1 1500
10
.1.0
.0/
24
Me
tric
10
10
.1.1
.0/
24
Me
tric
20
10.1.0.0/23
Metric 1
10.1.0.0/23
A
B
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Overlapping Summaries
EIGRP allows overlapping summaries
Set the administrative distance on the longer prefix so it is not installed...
Admin Distance of 255 is needed if the more specific summary actually matches a "real" prefix
interface serial 0/0 .... ip summary-address eigrp 1 10.1.0.0 255.255.0.0 ip summary-address eigrp 1 10.1.1.0 255.255.255.0 255
Interface serial 0/0 .... ip summary-address eigrp 1 10.1.0.0 255.255.0.0 ip summary-address eigrp 1 10.1.2.0 255.255.255.0 255
10.1.1.0/24 10.1.2.0/24
10.1.0.0/16
10
.1.0
.0/1
6
10
.1.0
.0/1
6
A B
C
10
.1.1
.0/2
4
10
.1.2
.0/2
4
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Overlapping Summaries
If two routing protocols provide a route to the same destination, how do we choose between them? Their metrics are not comparable
An administrative distance is added to each route learned based on the protocol installing the route
Static routes can be configured with a distance This can create a floating static
The route will not be used unless the dynamic protocols have no route to that destination
R1#show ip eigrp topology
P 10.0.1.0/24, 1 successors, FD is 2681856
via 10.1.1.1 (2681856/2169856)
R1(config)#ip route 10.0.1.0 255.255.255.0 null0
R1(config)#ip route 10.0.1.0 255.255.255.0 null0 200
distance 90
distance 1
distance 200
The static
route wins
The EIGRP
route wins
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Overlapping Summaries
EIGRP can leak more specific routes through a summary 12.3(11.01)T and later
route-map LeakList permit 10
match ip address 1
!
access-list 1 permit 10.1.2.0
!
interface Serial0/0
ip summary-address eigrp 1 10.1.0.0 255.255.0.0 leak-map LeakList
10.1.1.0/24 10.1.2.0/24
10.1.0.0/16
10
.1.0
.0/1
6
10
.1.0
.0/1
6
A B
C
10
.1.1
.0/2
4
10
.1.2
.0/2
4
route-map LeakList permit 10
match ip address 1
!
access-list 1 permit 10.1.1.0
!
interface Serial0/0
ip summary-address eigrp 1 10.1.0.0 255.255.0.0 leak-map LeakList
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Full routing information
Overlapping Summaries
Avoid creating summary black holes
Solution: have a link between the summarizing routers across which they share full routing information
10.1.1.0/24 10.1.2.0/24
10.1.0.0/16
A B
C
10
.1.0
.0/1
6
10
.1.0
.0/1
6
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Summary Routing Leaking
Route Summary Leaking
EIGRP allows user definable summary components to leak past the summary boundary
For optimal routing, we would like C to be able to receive as few routes as possible, but still optimally route to 10.1.1.0/24 and 10.1.2.0/24 dynamically
Combination of static routes and could be used but its difficult to maintain
The simplest way is to configure a leak-map on the summary route
10.1.1.0/24 10.1.2.0/24
10.1.0.0/16
10
.1.0
.0/1
6
10
.1.0
.0/1
6
route-map LeakList permit 10
match ip address 1
!
access-list 1 permit 10.1.1.0
!
router eigrp ROCKS
address-family ipv4 autonomous-system 4453
af-interface Serial0/0
summary-address 10.1.0.0 255.255.0.0 leak-map LeakList
A B
C
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Route-Map Support
EIGRP Route-Map Support
EIGRP supports Enhanced Route-Maps
Enhanced support of route maps allows EIGRP to use a route map to prefer one path over another
Route-maps can now be applied on the distribute-list in/out statement
Filters can be applied even before the prefix hits the topology table
route-map setmetric permit 10
match interface serial 0/0
set metric 1000 1 255 1 1500
route-map setmetric permit 20
match interface serial 0/1
set metric 2000 1 255 1 1500
....
router eigrp ROCKS
address-family ipv4 auto 4453
topology base
distribute-list route-map setmetric in
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Enhanced Routing Tagging
EIGRP Enhanced Route Tags
EIGRP has been extended to support a more flexible route tag method Dotted-Decimal notation easer to read
Support mask for multiple tag matching
Supports IPv4 and IPv6
Classic Route Tag route-map current-route-tag-usage permit 10
match tag 451580 451597 451614 451631
set metric 1100
!
Router# show ip route tag
Enhanced Route Tag ip access-list standard route-tag-mask
permit 100.160.60.60 0.0.3.3
!
route-map enhanced-route-tag permit 10
match ip address tag route-tag-mask
set metric 1100
!
Router# show ip route tag 100.160.61.60 0.0.3.3
Assigning routes a default tag router eigrp ROCKS
address-family ipv4 vrf tagit autonomous-system 4452
topology base
route-tag 100.160.61.61
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Distribution and Access
Distribution (aggregation point for access)
Summarization
Summary Metrics
Summary Leak-maps
Filtering
Route Map Support
Route Tag Enhancement
Access (STUB and edge features)
Managing alternate paths
Passive interfaces
Hub and Spoke
Scaling
Enhancements
Leak-maps
100
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Managing Wiring Closets
Alternative paths are a good thing.. Right?
Not if they are excessive OR undesired!
Alternative paths that exist in the network that provide little if any real benefit of improved reliability, and are often unplanned and unexpected.
In this example, the four Ethernets on the left are there to provide users with access to the network.
There are two routers connected to each VLAN in order to provide redundancy (probably via HSRP) so that the users will have failover capability if there is a problem.
1.1.1.0/24
A
B
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RtrA#show eigrp address-family ipv4 topo all | begin 1.1.1.0
P 1.1.1.0/24, 1 successors, FD is 128256, serno 2673915
via Connected, Loopback1
via 10.0.19.2 (9690112/9173248), FastEthernet6/0.19
via 10.0.20.2 (9690368/9173248), FastEthernet6/0.20
via 10.0.13.2 (9688576/9173248), FastEthernet6/0.13
via 10.0.45.2 (9696768/9173248), FastEthernet6/0.45
via 10.0.27.2 (9692160/9173248), FastEthernet6/0.27
via 10.0.28.2 (9692416/9173248), FastEthernet6/0.28
via 10.0.22.2 (9690880/9173248), FastEthernet6/0.22
via 10.0.42.2 (9696000/9173248), FastEthernet6/0.42
via 10.0.16.2 (9689344/9173248), FastEthernet6/0.16
via 10.0.10.2 (9687808/9173248), FastEthernet6/0.10
via 10.0.40.2 (9695488/9173248), FastEthernet6/0.40
via 10.0.21.2 (9690624/9173248), FastEthernet6/0.21
via 10.0.37.2 (9694720/9173248), FastEthernet6/0.37
via 10.0.41.2 (9695744/9173248), FastEthernet6/0.41
.snip.
Managing Wiring Closets
Unfortunately, the designer may have created a network topology a little different than what was intended
Wow, where did all
of these alternative paths
come from! for
a connected Route!
RtrA#show ip route | begin 1.1.1.0
C 1.1.1.0 is directly connected, Loopback1
.snip.
RtrA#show eigrp address-family ipv4 topo | begin 1.1.1.0
P 1.1.1.0/24, 1 successors, FD is 128256
via Connected, Loopback1
P 10.0.11.0/24, 1 successors, FD is 9048064
.snip.
B
1.1.1.0/24
A
B
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1.1.1.0/24
A
B
Each user segments will be treated as a possible alternative path!
Generally network designers generally do not have these user segments as transit paths
Each user segments is in the query path, causing EIGRP to do a lot of work by including these extra links.
Extra work means shower convergence.
A simple solution is provided with the use of
the passive-interface command.
Managing Wiring Closets
router eigrp 100
passive-interface fastethernet 0/0
passive-interface fastethernet 0/1
passive-interface fastethernet 0/2
passive-interface fastethernet 0/3
....
-or- router eigrp 100
passive-interface default
no passive-interface fastethernet 1/0
....
B
1.1.1.0/24
A
B
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Hub and Spoke (STUBs)
EIGRP Hub and Spoke (STUBs)
EIGRP offers the best scaling performance of all IGPs
If these spokes are remote sites, they have two connections for resiliency, not so they can transit traffic between A and B
A should never use the spokes as a path to anything, so theres no reason to learn about, or query for, routes through these spokes
What happens when a route or link is lost? EIGRP query's ALL neighbors
Each neighbors using it to reach the destination will also query their neighbors
B A
Dont Use These Paths
B A
10.1
.1.0
/24
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Hub and Spoke (STUBs)
Marking the spokes as stubs allows the STUBs to signal A and B that they are not valid transit paths
A will not query stubs, reducing the total number of queries in this example to one
Marking the remotes as stubs also reduces the complexity of this topology
Router B now believes it only has one path to 10.1.1.0/24 (through A), rather than five
B B A
10.1
.1.0
/24
router#config t
router(config)#router eigrp 100
router(config-router)#eigrp stub connected
router(config-router)#
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Hub and Spoke (STUBs)
If stub connected is configured B will advertise 10.1.2.0/24 to A
B will not advertise 10.1.2.0/23, 10.1.3.0/23, or 10.1.4.0/24
If stub summary is configured B will advertise 10.1.2.0/23 to A
B will not advertise 10.1.2.0/24, 10.1.3.0/24, or 10.1.4.0/24
ip route 10.1.4.0 255.255.255.0 10.1.1.10
!
interface serial 0
ip summary-address eigrp 10.1.2.0 255.255.254.0 5
!
router eigrp 100
redistribute static metric 1000 1 255 1 1500
network 10.2.2.2 0.0.0.1
network 10.1.2.0 0.0.0.255
eigrp stub connected
eigrp stub summary
10.1.2.0/24
10.2.2.2/31
10
.1.3
.0/2
4
A
B
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Hub and Spoke (STUBs)
If stub static is configured B will advertise 10.1.4.0/24 to A
B will not advertise 10.1.2.0/24, 10.1.2.0/23, or 10.1.3.0/24
If stub receive-only is configured B wont advertise anything to A,
so A needs to have a static route to the networks behind B to reach them
ip route 10.1.4.0 255.255.255.0 10.1.1.10
!
interface serial 0
ip summary-address eigrp 10.1.2.0 255.255.254.0
!
router eigrp 100
redistribute static 1000 1 255 1 1500
network 10.2.2.2 0.0.0.1
network 10.1.2.0 0.0.0.255
eigrp stub receive-only
eigrp stub static
10.1.2.0/24
10.2.2.2/31
10
.1.3
.0/2
4
A
B
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Hub and Spoke (STUBs)
If Stub Redistributed Is Configured
B will advertise 10.1.4.0/24 to A
B will not advertise 10.1.2.0/24, 10.1.2.0/23, or 10.1.3.0/24
ip route 10.1.4.0 255.255.255.0 10.1.1.10
!
interface serial 0
ip summary-address eigrp 10.1.2.0 255.255.254.0
!
router eigrp 100
redistribute static 1000 1 255 1 1500
network 10.2.2.2 0.0.0.1
network 10.1.2.0 0.0.0.255
eigrp stub redistributed
10.1.2.0/24
10.2.2.2/31
10
.1.3
.0/2
4
A
B
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Hub and Spoke (STUBs)
At A, you can tell B is a stub using show ip eigrp neighbor detail
router-a#show ip eigrp neighbor detail
IP-EIGRP neighbors for process 100
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 10.2.2.3 Se0 13 00:00:15 9 200 0 9
Version 12.4/1.2, Retrans: 0, Retries: 0, Prefixes: 1
Stub Peer Advertising ( CONNECTED ) Routes
Suppressing queries
10.1.2.0/24
10.2.2.2/31
10
.1.3
.0/2
4
A
B
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Hub and Spoke (STUBs)
At B, you can see that the EIGRP process for AS 100 is running as a stub using show ip protocols
router-b#show ip protocols
Routing Protocol is "eigrp 100"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Default networks flagged in outgoing updates
Default networks accepted from incoming updates
EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
EIGRP maximum hopcount 100
EIGRP maximum metric variance 1
EIGRP stub, connected
Redistributing: static, eigrp 100
.
.
10.1.2.0/24
10.2.2.2/31
10
.1.3
.0/2
4
A
B
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Hub and Spoke (STUBs)
Any combination of the route types can be specified on the eigrp stub statement, except receive-only, which cannot be used with any other option
For example: eigrp stub connected summary redistributed
If eigrp stub is specified without any options, it will enable eigrp stub connected summary
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Hub and Spoke Scaling
Most EIGRP Neighbors Seen 800 deployed in live, working networks
3500 is the largest number ever tested in a lab environment
Key Strategy for achieving scalability is design! Stub for EIGRP hub and spoke environments is a must
Minimize advertisements to spokes
Using summaries at the hubs with the new static summary metric option should increase scaling further still.
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Hub and Spoke Scaling
The blue line shows the rate at which the convergence time increases as EIGRP neighbors are added to hub routers and does not pass 500
The red line shows the convergence time if the neighbors added are all configured as EIGRP stub routers and scales to over 1000 peers
Measure initial bring up convergence until all neighbors are established and queues empty
Dual Homed Remotes, NPE-G1 with 1G RAM, 3000 prefixes advertised to each spoke
2
5
9
0 500 1000 1500
Number of Neighbors
Test performed with 12.3(14)T1
Non-Stub
EIGRP Stub
Tim
e (
min
ute
s)
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Hub and Spoke Failover
The blue line with the steep slope shows the rate at which the failover convergence time increases as EIGRP neighbors are added to a single hub router
The red line shows the failover convergence time if the neighbors added are all configured as EIGRP stub routers and is extremely linear in behavior
Primary Hub failed, time measured for EIGRP to complete failover convergence
Dual Homed Remotes, NPE-G1 with 1G RAM, 3000 prefixes advertised to each spoke
0
1
60
0 200 400 600 800 1000 1200 1400 1600
Number of Neighbors
Tim
e (
min
ute
s)
Test performed with 12.3(14)T1 15
EIGRP Stub
Non-Stub
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Stub Enhancements
Multipoint interface Enhancements
EIGRP Enhances Multi-point interface stability
When bringing up an interface with hundreds of neighbors, EIGRP may converge slowly, symptoms include;
Continuous neighbor resets
Packet retransmission timeout
Stuck-in-Actives
Hold time expirations
EIGRP uses the bandwidth on the main interface divided by the number of neighbors on that interface to get the bandwidth available per neighbor
Multipoint
tunnel
interface
Hub
Spoke-1 Spoke-n Spoke-2
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Stub Enhancements
Hub and spoke networks are often built over point-to-multipoint networks
If the hub is configured to treat the entire point-to-multipoint network as a single interface, it can transmit multicast and broadcast packets which are received by all spoke routers
Layer 3 on the hub router will not notice a single circuit failure
interface s0/0
ip address 10.1.1.1 255.255.255.0
Packets transmitted
here are received
only by the hub router
Packets tr