Configuring the Aging Time of Temporary ARP Entries

Context

In addition to generating ARP Miss messages, the device generates temporary ARP entries and sends ARP Request packets to the destination network.

In the aging time of temporary ARP entries:
- Before receiving an ARP reply packet, the device discards the IP packets matching the temporary ARP entry and does not generate ARP Miss messages.
- After receiving an ARP Reply packet, the device generates a correct ARP entry to replace the temporary entry.
When temporary ARP entries age out, the device clears them. If no ARP entries match the IP packets forwarded by the device, ARP Miss messages and temporary ARP entries are repeatedly generated.

You can rate-limit ARP Miss messages by setting the aging time of temporary ARP entries. When a device undergoes an ARP Miss attack, you can extend the aging time of temporary ARP entries to reduce the frequency of triggering ARP Miss messages so that the impact on the device is minimized.

Procedure

Run system-view
The system view is displayed.
Run interface interface-type interface-number
The interface view is displayed.
(Optional) On an Ethernet interface, run undo portswitch
The interface is switched to Layer 3 mode.

By default, an Ethernet interface works in Layer 2 mode.

Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
Run arp-fake expire-time expire-time
The aging time of temporary ARP entries is set.

By default, the aging time of temporary ARP entries is 3 seconds.