Configuring MAC Address Consistency Check in an ARP Packet

Context

The MAC address consistency check function for ARP packets prevents attacks from bogus ARP packets in which the source and destination MAC addresses are different from those in the Ethernet frame header. This function is usually configured on gateways.

This function enables the gateway to check the MAC address consistency in an ARP packet before ARP learning. If the source and destination MAC addresses in an ARP packet are different from those in the Ethernet frame header, the device discards the packet as an attack. If the source and destination MAC addresses in an ARP packet are the same as those in the Ethernet frame header, the device performs ARP learning.

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 validate { source-mac | destination-mac } ^*
MAC address consistency check in an ARP packet is enabled. This function compares the source and destination MAC addresses in ARP packets with those in the Ethernet frame header.

By default, MAC address consistency check in an ARP packet is disabled.

Sub-interfaces do not support the arp validate { source-mac | destination-mac }^* command. When receiving ARP packets, a sub-interface checks MAC address consistency based on the rule configured on the primary interface.

VLANIF interfaces do not support the arp validate { source-mac | destination-mac }^* command. When receiving ARP packets, a VLANIF interface checks MAC address consistency based on the rule configured on the member interface.