Whether you enable or disable ARP learning via gratuitous ARP, the system does not look up the target IP. It only updates the ARPentry for the Layer 3 interface with the source IP of the request.Configuring ARP RetriesIn Dell Networking OS versions prior to 8.3.1.0, the number of ARP retries is set to five and is not configurable. After five retries, DellNetworking OS backs off for 20 seconds before it sends a new request. Beginning with Dell Networking OS version 8.3.1.0, thenumber of ARP retries is configurable.The default backoff interval remains at 20 seconds.To set and display ARP retries, use the following commands.• Set the number of ARP retries.CONFIGURATION modearp retries numberThe default is 5.The range is from 1 to 20.• Set the exponential timer for resending unresolved ARPs.CONFIGURATION modearp backoff-timeThe default is 30.The range is from 1 to 3600.• Display all ARP entries learned via gratuitous ARP.EXEC Privilege modeshow arp retriesICMPFor diagnostics, the internet control message protocol (ICMP) provides routing information to end stations by choosing the bestroute (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 ICMPThe following lists the configuration tasks for ICMP.• Enabling ICMP Unreachable MessagesFor a complete listing of all commands related to ICMP, refer to the Dell Networking OS Command Line Reference Guide.Enabling ICMP Unreachable MessagesBy 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 modeno ip unreachableIPv4 Routing 327
