Reference Guide

472 | IPv4 Routing
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Figure 24-8. Learning via Gratuitous ARP
Whether ARP Learning via Gratuitous ARP is enabled or disabled, 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
The number of ARP retries is configurable. The default backoff interval is 20 seconds. 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) 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 Task List for ICMP
To configure ICMP, Enabling ICMP unreachable messages.
See the
Dell Networking OS Command Line Reference Guide for a complete listing of all commands related to
ICMP.
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
Host 1
IP: 1.1.1.2
MAC: AA
Host 2
IP: 1.1.1.3
MAC: BB
ARP Request
Target IP: 1.1.1.3
Target IP is not the VLAN interface
IP. Update existing Host 1 entry.
Drop packet.
VLAN ID: 1.1.1.1
X