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Concept Guide

ManualsBrandsDell ManualsAccess PlatformsPowerSwitch S4048T-ON
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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 trac.
Conguration Tasks for ICMP
The following lists the conguration tasks for ICMP.
• Enabling ICMP Unreachable Messages
For a complete listing of all commands related to ICMP, refer to the Dell EMC 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.
• To disable ICMP unreachable messages.
INTERFACE mode
no ip unreachable
• Set Dell EMC Networking OS 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.
ICMP Redirects
When a host sends a packet to a destination, it sends the packet to the congured default gateway. If the gateway router nds that a
better route is available through a dierent router in the same network, that is, the same data link, the gateway router sends the source
host an ICMP redirect message with the better route. The gateway router routes the packet to its destination and the host sends
subsequent packets to that particular destination through the correct router.
Dell EMC Networking OS supports both ICMP and ICMP6 redirect messages. The following diagram depicts a topology in which ICMP
redirect messages are useful.
IPv4 Routing
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