tb2380 retana transitioning from eigrp to ospf_final
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© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Transitioning Your Network From EIGRP To OSPFTB2380Alvaro Retana June 6, 2012
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
“When transitioning from one protocol to another there are lot of things to consider. In this session, attendees will hear a technical review of what to consider when transitioning from Enhanced Interior Gateway Routing Protocol (EIGRP) to Open Shortest Path First (OSPF). Attendees will gain a high-level overview of the protocols, network design considerations and more.”HP Discover 2012, Transitioning your network from EIGRP to OSPF
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.4
Agenda
MotivationIntroductionEIGRP and OSPF overviewNetwork architecture considerationsTransition strategies
Implementation considerationsInformation hidingInter-area routing informationTraffic flow
OSPF for IPv6
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.5
By insisting on open standards in your network your business can realize multiple benefits
Motivation: Why Migrate to a Standard ProtocolLower capital expense• A vendor who knows you cannot easily incorporate a competitor’s products into your
network is much less motivated at the bargaining table
Best-in-class solutions• Committing yourself to a single vendor using proprietary protocol sharply reduces your
ability to seek out the best product on the market for each function of your network
Lower risk• By diversifying your suppliers, you are less vulnerable to a single software malfunction
affecting your entire network• Your network is also less at risk of product obsolescence, vendor buyouts, or business
failures
Innovation• The most competitive enterprises see their network as a fundamental tool for business
innovation• Agility, adaptation, and flexibility are the key qualities that keep your network ahead of
your competitors
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Debunking The Myth Of a Single Vendor NetworkKey findings• No long term impact on OPEX• Lower TCO by at least 15-25% over five years• Multi vendor management tools ease the adoption of a second
vendor• Lasting decrease in network complexity
http://www.gartner.com/technology/media-products/reprints/hpprocurve/article7/article7.html
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Introduction
All you need to know in 4 slides!
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EIGRP and OSPF OverviewEnhanced Interior Gateway Protocol (EIGRP)
Open Shortest Path First (OSPF)
Standardization status
• Never submitted to any standards body • Standardized by the IETF• OSPFv2 = rfc2328
Routing algorithm
• Diffusing Update Algorithm (DUAL)• Developed at SRI International• DUAL guarantees 100% loop free paths• Sub-second convergence can be achieved
in the presence of feasible successors (no tuning needed)
• Dijkstra Shortest Path First (SPF)• Developed by Dr. Edsger Dijkstra in 1956• SPF and strict inter-area propagation rules
guarantee 100% loop free paths• Sub-second convergence can be obtained
through tuning or the use of IP Fast Reroute
Summarization and hierarchy
• Auto-summarization at major network boundaries
• Manual summarization at any point in the network
• Supports multiple levels of hierarchy• No topology information carried
• Manual Route Summarization and Automatic Topology Aggregation at area borders
• Supports two levels of hierarchy• Carries intra-area topology information
Metrics and load sharing
• Composite metric that can consider bandwidth, delay, load, reliability and MTU
• Can load share over both equal and unequal cost paths
• Path cost is derived from the link bandwidth• Can load share over equal cost paths
IPv6 support • Supported in a separate instance • OSPFv3 (rfc5340) was developed for IPv6 support
• Extensions exist to carry IPv4 in a separate instance
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Network Architecture Considerations
Hierarchy structure & addressing schemeEIGRP allows for unlimited hierarchy levels, defined by the location of summarization points (manual or automatic)
− Route summarization is allowed at any router
OSPF allows for two levels of strict hierarchy, defined by the placement of areas
− Route summarization is allowed only at Area Border Routers (ABR)
− The topology is automatically aggregated
In general, the placement and type of an OSPF area should directly match the location and policies at the EIGRP
summarization points
EIGRP summarization points
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Transition Strategies
Flash transition / overlay1. Configure OSPF on the network with a high administrative distance2. Verify the OSPF routing information
• The routes may not match if the EIGRP design used multiple summarization points
3. Lower the OSPF administrative distance• The routing table should now contain only OSPF routes
4. Remove EIGRP from the network
EIGRP EIGRPEIGRPOSPF OSPFOSPF
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Transition Strategies (2)
Coexistence (redistribution)1. Configure mutual redistribution at the border between OSPF and EIGRP
network regions• Coexistence may be temporary while different regions are transitioned
OSPF
EIGRP EIGRP EIGRP
OSPF OSPFRedistribution Redistribution
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Implementation Considerations
That was easy!! Are there other details to consider?
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Information Hiding
Route summarization and topology aggregation are two common mechanisms that result in the reduction of information propagated throughout the network• EIGRP doesn’t carry topology information • The topology knowledge at any router is limited to its directly connected
neighbors• Route summarization can be configured at any point in the network• OSPF Area Border Routers (ABR) aggregate the topology and (can)
summarize the routing information• Every router knows the full topology of the local area• Route summarization can only occur at an ABR or ASBR
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OSPF as a Distance Vector Protocol
Routing information is propagated between areas only when it is being usedOnly intra-area OSPF information in the routing table is converted to inter-area summary LSAs and sent to the backbone (Area 0)
Effect1. Before the transition, only Intra-area information will be present in the OSPF
database2. During the transition, redistribution may be needed – especially when
converting one area at a time
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Intra-area Routing Considerations
EIGRP doesn’t have the concept of areas, which result in no limitations on the traffic flow patterns across the network
OSPF always prefers intra-area routes, so the placement of area boundaries may affect the existing traffic flow
100G
100G
100G100G
1G
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EIGRP Traffic Flow
Metric = BW + delay
100G
100G
100G100G
1G
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OSPF Traffic Flow
100G Link in Area 1
100G
100G
100G100G
1G
Area 1
Area 0
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OSPF Traffic Flow (2)
100G Link in Area 0
100G
100G
100G100G
1G
Area 1
Area 0
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OSPF Area Placement
Potential solutions1. Use a virtual link: place the 100G link in both areas2. Add more parallel 100G links, so that at least one is in each area3. Implement OSPF in a single-area configuration
© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
OSPF for IPv6
OSPFv2 = IPv4OSPFv3 = IPv6
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OSPF Evolution
Origin
al OSPF
spec
ifica
tion p
ublished
1989
OSPFv2
was
firs
t
published
1991
OSPF fo
r IPv
6 (aka
OSPF
v3)
was fi
rst p
ublished
1999
RFC 5
340
(OSP
F fo
r IPv
6)
2008
RFC 5
838 (Addre
ss
Fam
ilies i
n OSPF
v3)
2010
RFC 2
328 (OSPF
v2)
1998
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OSPFv3 and v2 Similarities
• The same 5 packet types but some fields have been changed
• Mechanisms for neighbor discovery and adjacency formation
• Interface types• P2P, P2MP, Broadcast, NBMA, Virtual
• LSA flooding and aging• DR, BDR election, area support, SPF• Nearly identical LSA types
Packet type12345
Link state updateLink state acknowledgment
DescriptionHelloDatabase descriptionLink state request
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OSPFv3 and OSPFv2 Differences
• Changes made to OSPFv2 to accommodate increased address size of IPv6• OSPF now runs on per-link, not per-subnet• Removal of addressing semantics from OSPF packets and LSAs making it network
protocol independent• New LSAs created to carry IPv6 addresses and prefixes • Addition of flooding scope (similar to RFC2370)• Explicit support for multiple instances per link• Use of IPv6 link-local addresses for protocol processing and providing next hop
information during packet forwarding• Authentication method changes• Packet format & LSA’s header format changes • Handling of unknown LSA types
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OSPFv2 had two flooding scopes• AS wide• Area wide
OSPFv3 has three flooding scopes:• AS scope - LSA is flooded throughout the AS• Area scope - LSA is flooded only within an area• Link-local scope - LSA is flooded only on the local link
OSPFv3 Flooding Scope
LS age U S2 S1 LSA Function Code
LS age Options LS type
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OSPFv3 Flooding ScopeU (unrecognized) bit is used to indicate to a router how to handle an LSA if it is unrecognized
S2 / S1 bit indicates the three flooding scopes
S2 S10 00 11 01 1
Flooding scopeLink-local flooding scopeArea flooding scopeAS flooding scopeReserved
U-bit01
Treat this LSA as if it has link-local ScopeStore and flood this LSA as if type understood
LSA handling
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OSPFv3 LSA Types
List of LSAs in OSPFv3
LSA name LS type code Flooding scope LSA function codeRouter LSA 0x2001 Area scope 1Network LSA 0x2002 Area scope 2Inter-Area-Prefix-LSA 0x2003 Area scope 3Inter-Area-Router-LSA 0x2004 Area scope 4AS-External-LSA 0x4005 AS scope 5Group-membership-LSA 0x2006 Area scope 6Type-7-LSA 0x2007 Area scope 7Link-LSA 0x0008 Link-local scope 8Intra-Area-Prefix-LSA 0x2009 Area scope 9
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Dual-stack OSPF Deployment
Multi-instanceMultiple instances of OSPF on a given linkEnhances the ability to isolate the resources associated with both router and networkInstance specific prioritization for PDUs and routing calculations
Convergence considerationsIGPs will compete over processor cycles based on their relative tuning• If you configure the IPv4 and IPv6 IGPs the same way (aggressively tuned for fast
convergence), naturally expect a doubling of their stand-alone operation convergence time
• If the IPv6 IGP is operating under default settings, the convergence time for the optimally tuned IPv4 IGP is not significantly affected
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Conclusions / Summary
By insisting on open standards in your network your business can realize multiple benefits
It is important to understand the differences in routing protocol operation and the implications on the current network before starting a transition• Location of summarization points• Network hierarchy• Metrics, load sharing and traffic flow• Information propagation: topology and reachability information• Transition mechanisms (and which one is best for your network)• Protocol evolution
Always the best protocol is the one which is right for your network
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Tools to Help Our Clients • Read about the FlexNetwork Architecture
• Learn about Virtual Application Networks
• Discover Intelligent Management Center
• View the HPN Portfolio Matrix Guide
• Learn about networking services from HP Technical Services
• Learn about networking career certifications from HP ExpertONE
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After the eventVisit these demos
Find out more
Attend these sessions
• TB2375, Simplify large scale secure WAN deployments, Wednesday @ 4pm
• TB3244, IPv6 Deployment: Understanding internal IPV6 protocols, Tuesday @ 4pm
• HP Flex Network Architecture
• A holistic approach to IPV6
• Dynamic Virtual Private Network (DVPN)
• Contact your sales rep
• Visit the HP Networking website at: http://www.hp.com/networking
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© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.© Copyright 2012 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Q&A
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