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ARP Gateway Anti-Collision
As shown in Figure 10-5, attacker B forges the gateway address to send a bogus ARP packet to user A. User A considers the attacker to be the gateway. User A then records an incorrect ARP entry for the gateway. As a result, the gateway cannot receive packets from user A and their communication is interrupted.
To defend against bogus gateways, you can enable the ARP bogus gateway attack defense function on gateways directly connected to the host. Such gateways must meet the following conditions:
- A VLANIF or VBDIF interface is used to receive packets.
- The source IP address of received packets is the same as the IP address of the inbound interface.
- The source MAC address of the Ethernet header in received packets is different from the source MAC address of ARP packets or the interface MAC address.
- The source MAC address of received packets is not a virtual MAC address of the Virtual Router Redundancy Protocol (VRRP) group.
A VRRP group, also called a virtual router, serves as the default gateway for hosts on a LAN. A virtual router has a virtual MAC address that is generated based on the virtual router ID. The virtual MAC address is in the format of 00-00-5E-00-01-{VRID}(VRRP). The virtual router sends ARP Reply packets using the virtual MAC address instead of the interface MAC address.
