Users Guide

ARP Learning via Gratuitous ARP
Gratuitous ARP can mean an ARP request or reply.
In the context of ARP learning via gratuitous ARP on Dell EMC Networking OS, the gratuitous ARP is a request. A gratuitous
ARP request is an ARP request that is not needed according to the ARP specification, but one that hosts may send to:
● detect IP address conflicts
● inform switches of their presence on a port so that packets can be forwarded
● update the ARP table of other nodes on the network in case of an address change
In the request, the host uses its own IP address in the Sender Protocol Address and Target Protocol Address fields.
Enabling ARP Learning via Gratuitous ARP
To enable ARP learning via gratuitous ARP, use the following command.
● Enable ARP learning via gratuitous ARP.
CONFIGURATION mode
arp learn-enable
ARP Learning via ARP Request
In Dell EMC Networking OS versions prior to 8.3.1.0, Dell EMC Networking OS learns via ARP requests only if the target IP
specified in the packet matches the IP address of the receiving router interface. This is the case when a host is attempting to
resolve the gateway address.
If the target IP does not match the incoming interface, the packet is dropped. If there is an existing entry for the requesting
host, it is updated.
Figure 49. ARP Learning via ARP Request
Beginning with Dell EMC Networking OS version 8.3.1.0, when you enable ARP learning via gratuitous ARP, the system installs a
new ARP entry, or updates an existing entry for all received ARP requests.
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IPv4 Routing