Configuring MAC Address-Triggered ARP Entry Update to Improve VRRP Switchover Performance

In scenarios where a Virtual Router Redundancy Protocol (VRRP) group connects to servers, MAC address-triggered ARP entry update can be configured to speed up VRRP active/standby switchovers. This function minimizes the service interruption time if a link or switch fails.

VRRP groups multiple routing devices into a virtual router, which functions as the virtual gateway for users. Its virtual IP address is used as the default gateway address to implement communication with an external network. If a gateway fails, VRRP selects another gateway to transmit service traffic, ensuring reliable communication.

In Figure 1, HostA is dual-homed to SwitchA and SwitchB through the switch. A VRRP group is configured on SwitchA and SwitchB to implement link redundancy. If the link between SwitchA and the switch fails, MAC address entries and ARP entries on the switch are updated to ensure that traffic is switched to the link between the switch and SwitchB.

Figure 1 VRRP networking

A VRRP group may connect to a server but not a switch, as shown in Figure 2. Generally, a server selects only one network interface to send packets. When the server detects a network failure or traffic transmission failure, it sends packets through another network interface.

SwitchA functions as the master device, and the server uses Port2 to send packets. SwitchA learns the ARP entry and MAC address entry matching the server on Port2, and SwitchB learns the server MAC address on Port1.
When the server detects that Port2 is faulty, the server sends packets through Port1. SwitchA then learns the server MAC address on Port1. If the server does not send an ARP Request packet to SwitchA, SwitchA still maintains the ARP entry on Port2. In this case, packets sent from SwitchA to the server are still forwarded through Port2 until the ARP entry is aged out.

To address the preceding issue, configure MAC address-triggered ARP entry update on the switches. This function enables the switches to update the corresponding ARP entry when the outbound interface in a MAC address entry changes.

Figure 2 VRRP group connecting to a server