IRDP Protocol Configuration

IRDP Protocol –

ICMP Router Discovery Protocol (IRDP) is First Hop Redundancy Protocol (FHRP) for hosts to discover the presence and location of routers on their IPv4 [p2p type=”slug” value=”what-is-local-area-network”]LAN[/p2p] network. The IRDP is defined by the IETF RFC 1256 standard.

IRDP eliminates the need to manually configure routing information.[p2p type=”slug” value=”internet-control-message-protocol-icmp”]ICMP[/p2p] protocol is leveraged in IRDP.

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Below is a scenario where IRDP is configured across 2 Routers and depicts the failover across the IRDP enabled Routers –

irdp protocol

R1 will be configured as host devices. IP Routing will be disabled to make it behave as end system as below –

R1(config)#no ip routing
R1(config)#ip gdp irdp

Now , R2 will be configured with IRDP configuration on Interface Fa0/0. And given high preference of 100 to behave as default gateway for hosts.

R2#config t
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#int fa0/0
R2(config-if)#
interface FastEthernet0/0
ip address 192.168.23.2 255.255.255.0
ip irdp
ip irdp maxadvertinterval 5
ip irdp minadvertinterval 3
ip irdp holdtime 5
ip irdp address 192.168.23.2 100

The same way as R2 , R3 is also configured for irdp on interface Fa0/0 however as backup default Router by giving lower preference of 90.

R3(config)#int fa0/0
R3(config-if)#
interface FastEthernet0/0
ip address 192.168.23.3 255.255.255.0
ip irdp
ip irdp maxadvertinterval 5
ip irdp minadvertinterval 3
ip irdp holdtime
ip irdp address 192.168.23.3 90

Now that IRDP is complete, we will try to ping R4 Router Loopback IP of 4.4.4.4 and see IRDP normal scenario and failover function.

In Normal scenario traffic from Host R1 destined towards R4 Loopback (4.4.4.4) shall take path through IRDP router with higher prefernce and in this case its R2 (Preference 100)

R1#traceroute 4.4.4.4
Type escape sequence to abort.
Tracing the route to 4.4.4.4
1 192.168.23.2 96 msec 60 msec 60 msec
2 192.168.24.4 120 msec 124 msec 124 msec

Now we will shut interafce fa0/0 of R2

R2(config)#int fa0/0
R2(config-if)#shut

When the primary path is shut , traffic from R1 will take backup path via IRDP Router R3 with preference of 90 as shown below –

R1#traceroute 4.4.4.4
Type escape sequence to abort.
Tracing the route to 4.4.4.4
1 192.168.23.3 88 msec 40 msec 68 msec
2 192.168.34.4 124 msec 92 msec 100 msec
R1#

From this lab scenario, we understood how IRDP performs FHRP functionality and provides redundancy to endpoints.

To know more about IRDP protocol watch this video –

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