Users Guide

Figure 50. ARP Learning via ARP Request with ARP Learning via Gratuitous ARP Enabled
Whether you enable or disable ARP learning via gratuitous ARP, the system does not look up the target IP. It only updates the ARP entry
for the Layer 3 interface with the source IP of the request.
Configuring ARP Retries
You can configure the number of ARP retries.
The default backoff interval remains at 20 seconds. On the device, 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 time increase reduces the potential
for the system to slow down while waiting for a multitude of ARP responses.
To set and display ARP retries, use the following commands.
• Set the number of ARP retries.
CONFIGURATION mode
arp retries number
The default is 5.
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
For a complete listing of all commands related to ICMP, refer to the Dell Networking OS Command Line Reference Guide.
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IPv4 Routing