Reference Guide

The range is from 1 to 20.
• Set the exponential timer for resending unresolved ARPs.
CONFIGURATION mode
arp backoff-time
The default is 30.
The range is from 1 to 3600.
• Display all ARP entries learned via gratuitous ARP.
EXEC Privilege mode
show arp retries
ICMP
For diagnostics, the internet control message protocol (ICMP) provides routing information to end stations by choosing
the best route (ICMP redirect messages) or determining if a router is reachable (ICMP Echo or Echo Reply).
ICMP error messages inform the router of problems in a particular packet. These messages are sent only on unicast
traffic.
Configuration Tasks for ICMP
The following lists the configuration tasks for ICMP.
• Enabling ICMP Unreachable Messages
• Enabling ICMP Redirects
For a complete listing of all commands related to ICMP, refer to the FTOS Command Line Reference Guide .
Enabling ICMP Unreachable Messages
By default, ICMP unreachable messages are disabled.
When enabled, ICMP unreachable messages are created and sent out all interfaces.
To disable and re-enable ICMP unreachable messages, use the following commands.
• To disable ICMP unreachable messages.
INTERFACE mode
no ip unreachable
• Set FTOS to create and send ICMP unreachable messages on the interface.
INTERFACE mode
ip unreachable
To view if ICMP unreachable messages are sent on the interface, use the show config command in INTERFACE
mode. If it is not listed in the show config command output, it is enabled. Only non-default information is displayed in
the
show config command output.
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