mac-address update arp
Function
The mac-address update arp command enables the MAC address-triggered ARP entry update function. That is, the Switch is enabled to update outbound interfaces in ARP entries when outbound interfaces in MAC address entries change.
The undo mac-address update arp command disables the MAC address-triggered ARP entry update function.
By default, the MAC address-triggered ARP entry update function is disabled.
Format
mac-address update arp
undo mac-address update arp
Only the S5720-EI, S5720-HI, S5720I-SI, S5720S-SI, S5720-SI, S5735-S, S5735S-S, S5735-S-I, S5730-HI, S5730S-EI, S5730-SI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S5720-LI, S5720S-LI, S6720-LI, S6720S-LI, S6720-EI, S6720-HI, S6720S-EI, S6720S-SI, S6720-SI, S6730-H, S6730S-H, S6730-S, and S6730S-S support this command.
Usage Guidelines
Usage Scenario
On the Ethernet, MAC address entries are used to guide Layer 2 data forwarding. The ARP entries that define the mapping between IP addresses and MAC addresses guide communication between devices on different network segments.
The outbound interface in a MAC address entry is updated by packets, whereas the outbound interface in an ARP entry is updated after the aging time is reached. In this case, the outbound interfaces in the MAC address entry and ARP entry may be different. To address this issue, run the mac-address update arp command to enable the Switch to update outbound interfaces in ARP entries when outbound interfaces in MAC address entries change.
Precautions
This command takes effect only for dynamic ARP entries. Static ARP entries are not updated when the corresponding MAC address entries change.
The mac-address update arp command does not take effect after ARP entry fixing is enabled by using the arp anti-attack entry-check { fixed-mac | fixed-all | send-ack } enable command.
After the mac-address update arp command is run, the Switch updates an ARP entry only if the outbound interface in the corresponding MAC address entry changes.
After this command is executed, the arp anti-attack gratuitous-arp drop command becomes invalid and the Switch cannot drop gratuitous ARP packets.