Reference Guide

IPv4 Routing | 429
Configurable ARP Retries
In FTOS versions prior to 8.3.1.0 the number of ARP retries is set to 5 and is not configurable. After 5
retries, FTOS backs off for 20 seconds before it sends a new request. Beginning with FTOS version
8.3.1.0, the number of ARP retries is configurable.
The default backoff interval remains at 20 seconds. On the S4810 platform, with FTOS version 8.3.8.0 and
later, the time between ARP resend is configurable. This timer is an exponential backoff timer. Over the
specified period, the time between ARP requests increases. This reduces the potential for the system to
slow down while waiting for a multitude of ARP responses.
ICMP
For diagnostics, Internet Control Message Protocol (ICMP) provide 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 Task List for ICMP
Use the following steps to configure ICMP:
• Enable ICMP unreachable messages on page 429
• Enable ICMP redirects on page 430
See the for a complete listing of all commands related to ICMP.
Enable ICMP unreachable messages
By default, ICMP unreachable messages are disabled. When enabled ICMP unreachable messages are
created and sent out all interfaces. To disable ICMP unreachable messages, use the
no ip unreachable
command.
Task Command Syntax Command Mode
Set the number of ARP retries.
arp retries number
Default: 5
Range: 1-20
CONFIGURATION
Set the an exponential timer for resending unresolved
ARPs.
arp backoff-time
Default: 30
Range: 1 to 3600
CONFIGURATION
Display all ARP entries learned via gratuitous ARP.
show arp retries EXEC Privilege