Administrator Guide

• 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
For a complete listing of all commands related to ICMP, refer to the Dell Networking OS 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.
• Set the system 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.
UDP Helper
User datagram protocol (UDP) helper allows you to direct the forwarding IP/UDP broadcast traffic by creating
special broadcast addresses and rewriting the destination IP address of packets to match those addresses.
Configure UDP Helper
Configuring the system to direct UDP broadcast is a one-step process:
IPv4 Routing 461