Tuesday, August 16, 2011

Configuring FHRP - IRDP

The less known, the unpopular, the quiet and the secretive protocol of First Hop Redundancy Protocol (FHRP) is ... dun dun dun .. IRDP (ICMP Router Discovery Protocol). In this blogtorial we will configure IRDP which uses 'ICMP' to send the default gateway information to hosts. This will be a short and simple blogtorial so consider the topology below and let's get started.

Objectives:
  • Configure R1 and R2 to with IRDP
  • R1 should be the primary default gateway and R2 should be the backup default gateway
  • R2 should take over when R1 goes down
Relevant configurations are posted below. 


First let's see how we can configure R1 and R2. Notice the 'irdp address preference ##' Routers with higher preference will be chosen by the hosts as its default gateway. 


Simple enough. Now let's take a look at R3. To emulate a host we need to disable routing on R3 using 'no ip routing' and enable 'ip irdp' on the appropriate interface also we need to enable 'ip gdp irdp'.




Note that the default gateway is 192.168.1.1 because of the higher preference.
So that's it .. quick and easy -- irdp configuration is done. 

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