Configuring ARP Packet Validity Check

Context

To avoid ARP attacks, you can enable ARP packet validity check on an access device or a gateway to filter out ARP packets with invalid IP addresses or MAC addresses. The device checks validity of an ARP packet based on each or any combination of the following items:

Source and destination IP addresses: The device checks the source and destination IP addresses in an ARP packet. If the source or destination IP address is all 0s, all 1s, or a multicast IP address, the device discards the packet as an invalid packet. The device checks both the source and destination IP addresses in an ARP Reply packet but checks only the source IP address in an ARP Request packet.
Source MAC address: The device compares the source MAC address in an ARP packet with that in the Ethernet frame header. If they are the same, the packet is valid. If they are different, the device discards the packet.
Destination MAC address: The device compares the destination MAC address in an ARP Reply packet with that in the Ethernet frame header. If they are the same, the packet is valid. If they are different, the device discards the packet.

Generally, the ARP protocol allows both an ARP packet whose source MAC address is different from that in the Ethernet frame header, and an ARP Reply packet whose destination MAC address is different from that in the Ethernet frame header. When an attack occurs, capture and analyze packets. If the attack is initiated by using inconsistent source or destination MAC addresses in the ARP packet and Ethernet frame header, enable ARP packet validity check based on the source or destination MAC address.

Procedure

Run system-view
The system view is displayed.
Run arp anti-attack packet-check { ip | dst-mac | sender-mac } ^*
ARP packet validity check is enabled and check items are specified.

By default, ARP packet validity check is disabled.

If you run the arp anti-attack packet-check { ip | dst-mac | sender-mac }^* command multiple times, all the check items specified in these commands take effect.