Content

| 6.2 |  | Implementing Router Redundancy in a Switched Network |
| 6.2.2 |  | ICMP Router Discovery Protocol (IRDP) |

Some newer IP hosts use IRDP (RFC 1256) to find a new router when a route becomes unavailable. A host that uses IRDP listens for hello multicast messages from the router that the host is configured to use. The host switches to an alternate router when the host no longer receives those hello messages. IRDP has a default advertisement rate of once every seven to ten minutes. The default lifetime is 30 minutes. These default timer values mean IRDP is not suitable to detect first-hop failures.

Enabling IRDP Processing
The only required task for configuring IRDP routing on a specified interface is to enable IRDP processing on an interface. Use the following command in interface configuration mode:

> ip irdp

When enabling IRDP processing, the default parameters will apply. To optionally change any of these IRDP parameters, use the commands listed in Figure while in interface configuration mode.

To display IRDP values, use the command show ip irdp

Troubleshooting IRDP
Use the debug ip icmp command to display information on ICMP transactions. This command helps determine whether the router is sending or receiving ICMP messages. Use this command when troubleshooting an end-to-end connection problem. The no form of this command disables debugging output.

> Router#no debug ip icmp