Reference Guide

Figure 48. ARP Learning via ARP Request
Beginning with FTOS 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.
Figure 49. 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
In FTOS versions prior to 8.3.1.0, the number of ARP retries is set to five and is not configurable. After five retries, FTOS
backs off for 20 seconds before it sends a new request. Beginning with FTOS version 8.3.1.0, the number of ARP retries is
configurable.
The default backoff interval remains at 20 seconds. On the S4820T, with FTOS version 8.3.8.0 and later, 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.
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