Administrator Guide

In Dell Networking OS versions prior to 8.3.1.0, if a gratuitous ARP is received some time after an ARP
request is sent, only RP2 installs the ARP information. For example:
1. At time t=0 Dell Networking OS sends an ARP request for IP A.B.C.D
2. At time t=1 Dell Networking OS receives an ARP request for IP A.B.C.D
3. At time t=2 Dell Networking OS installs an ARP entry for A.B.C.D only on RP2.
Beginning with Dell Networking OS version 8.3.1.0, when a gratuitous ARP is received, Dell Networking
OS installs an ARP entry on all three CPUs.
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 Networking OS versions prior to 8.3.1.0, Dell 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 36. ARP Learning via ARP Request
Beginning with Dell 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.
IPv4 Routing
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