Dynamic Routing•With the help of Routing Protocols Router find the way by itself is called

Dynamic Routing

• Routing Protocols are divided into two:-• Interior gateway protocol• Exterior gateway protocol Interior gateway Protocols are used in an autonomous system and Exterior gateway protocols are to configure ASBR.

• Ex: of Interior Gateway- RIP, IGRP, EIGRP, OSPF

• Ex: of Exterior Gateway- BGP, IS-IS

• Terms in Dynamic routing…

Autonomous System• A group of Routers in a single administrative domain is called autonomous

system.

• Autonomous systems consisting of same number can communicate.

• Different autonomous system is inter connected using ASBR (Autonomous System Boundary Router)

Administrative Distance• If a network gets an information from a source through multiple Router, it

selects the Router having lowest Administrative Distance value.

• RIP- 120

• IGRP- 100

• OSPF-110

• EEGRP- 90

DVP (Distance Vector Protocol)• Factors which is used in DVP are Distance & Direction for communication

between two networks

• Each Router has a routing table which it shares with other Routers i.e., each Router updates its routing table in every periodic timers

• If one of the network under a Router becomes down all other updates their routing table.

• Due to this convergence a looping occurs called Routing Loop.

• This is not applicable in most cases.

Maximum Hop Count• It is a loop avoiding technique

• It counts hop in every table

• After a critical no: of hop it avoids before looping occurs

Split Horizon• It is also a loop avoiding system

• If a Router R1 updates a network information from another Router R2

• Then that network information is not updates back in the R1

Reverse Poison• The Router under which the network is down produces a signal called reverse

poison.

• It shares with other Routers.

• It removes the information regarding the network which is down on the other Routers.

Hold down Timer• If a network is down under a flappy situation under a Router, the hold down timer waits for a

particular time period.

• After that it removes the information regarding the down network in the other Routers.

RIP (Routing Information Protocol)• RIP is a universal protocol.

• Could be configured in any Router.

• Its AD value is 120.

• It is DVP.

• RIP’s metric is hop count.

• RIP’s hop count is 15, so it supports up to 16 Routers.

• It has two versions, RIP version 1 and RIP version 2

• Providing sub netted IP’s for Router in order to avoid wastage of IP is called RIP version 2.

• RIP version 2 is classless routing protocol.

RIP Configuration

An example of a routing configuration is:

Router(config)#Router rip

Router(config-Router)#network 172.16.0.0

Verifying RIP

RIP Timers• Route update timer Sets the interval (typically 30 seconds) between periodic routing

updates

• Route invalid timer Determines the length of time (180 seconds) before a Router determines that a route has become invalid

• Hold-down timer This sets the amount of time during which routing information is suppressed. This continues until either an update packet is received with a better metric or until the hold-down timer expires. The default is 180 seconds

• Route flush timer Sets the time between a route becoming invalid and its removal from the routing table (240 seconds).

• Syntax:-

Router(config-Router)#timers basics 10 20 30 40

Debugging

Passive InterfacePassive-interface command prevents RIP update broadcasts from being sent out a defined interface, but same interface can still receive RIP updates

R1#config tR1(config)#Router ripR1(config-Router)#network 192.168.10.0R1(config-Router)#passive-interface serial 0

IP Routing Table

RIP version 1 vs. RIP version 2

R1# config tR1(config)# )#Router ripR1(config)#network 192.168.10.0R1(config)#network 192.168.20.0R1(config)#version 2

Floating type AD value• Configured two protocols in a network RIP & Static, but should work only on RIP.

• For that we increase Static’s AD value larger than the RIP.

• If RIP is down it should work on Static.

• Syntax:-

Router(config)#ip route ‘unknown network’ ‘subnet mask’ ‘next hop address’ ‘ad value’

IGRP (Interior Gateway Protocol)• It is a distance vector protocol

• It is a cisco proprietary protocol

• Only works on cisco devices

• Its AD value is 100

• IGRP metric is composite metric

• There are 5 factors to find the direction

1. Bandwidth

2. Delay

3. Load

4. Reliability

5. MTU (Maximum Transmission Unit)

• Default Hop count is 100

• It could be extended up to 255.

Configuring IGRP

IGRP Timers• Update timers these specify how frequently routing-update messages should be sent. The

default is 90 seconds.

• Invalid timers These specify how long a Router should wait before declaring a route invalid if it doesn’t receive a specific update about it. The default is 3*90 = 270.

• Hold-down timers These specify the hold-down period. The default is three times the update timer period plus 10 seconds. 280 seconds

• Flush timers These indicate how much time should pass before a route should be flushed from the routing table. The default is seven times the routing update period. If the update timer is 90 seconds by default, then 7 × 90 = 630 seconds elapse before a route will be flushed from the route table.

EIGRP (Enhanced Interior Gateway Routing Protocol)• EIGRP is a Cisco proprietary protocol

• Its is a hybrid protocol

• It has Features of Link state and DVP

• It maintains three tables:-

1. Neighbor ship- This table keeps the information of another Router which is its neighbor.

2. Topology- It keeps the information of all possible routes from one network to another.

3. Routing- This keeps the information of best path from one n/w to another.

• It has AD value of 90

• Distance is calculated by composite metric

• Its maximum hop count is 100, extendable up to 255

Efficient Neighbor Discovery• Hello packet is used to establish neighbor ship by Router.

• Every 5 sec Hello packet is sent to 224.0.0.10

• When another Router receives the hello packet, it checks whether it is in same network or in same AS no: or same K values.

• Then only it sends acknowledgement and Accepts the Router as its neighbor

• This process is called efficient neighbor discovery.

RTP (Reliable Transport Protocol )• This protocol is enhanced with EIGRP

• If a Router is down and another Router does not receives any acknowledgement

• It sends the hello packet as unicast 16 times to the Router

• Still if does not receives any acknowledgement, the it removes the information regarding the Router from neighbor ship table.

PDM (Protocol Dependent Module)It is module which helps to communicate multiple or different types of network protocol or IOS

Reporter

• If R1 receives the information regarding R3 network from R2.

• Then R2 is the reporter.

Reported Distance

• The Distance from Reporter to R3 network is called Reported Distance.

Feasible Distance

The distance from R1 to the Reporter + the Reported Distance is called Feasible Distance or Actual Distance.

Successor

• Routing table which consist of information regarding the best path from one network to another is called Successor

Feasible Successor

• The second best path in Routing table is called Feasible Successor.

DUAL (Diffusing Update Algorithm)• All route computations in EIGRP are handled by DUAL

• One of DUAL's tasks is maintaining a table of loop-free paths to every destination.

• It is used in EIGRP .

• It manages the best path and best second path.

Configuring EIGRP

Router(config)#router eigrp autonomous-system

Router(config-router)#network ‘network address’

EIGRP & IGRP Metric Calculation

To view Tables• Neighbor ship table- Router#show ip eigrp neighbors

• Topology table- Router#show ip eigrp topology

• Routing- Router#show ip route

Summarization• Super netting is the reverse process of sub netting

• It is the process of converting multiple network to a single network

• There are two types:-

1. Automatic

2. Manual

• Automatic Summarization is enabled in default Cisco router

• It is summarized to parent network.

• Syntax:-

Router(config-router)#no auto-summary

• Summary address is given to the interface at which all the updates are sharing.

• Router(config-if)#ip summary –address eigrp 100 ‘address’ ‘mask’

Loopback Interface• Virtual or imaginary interface configuration for router

• Syntax:-

Router(config)#interface loopback 0

Router(config-if)#ip address ‘address’ ‘mask’

Router(config-if)#no shut