Configuring MAC Address-Triggered ARP Entry Update to Improve VRRP Switchover Performance
When a VRRP group is connected to servers, you can configure MAC address-triggered ARP entry update to speed up VRRP active/standby switchovers. This function can reduce the service interruption time when a link or device fails.
In Figure 2-10, 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.
In Figure 2-11, a server is connected to a VRRP group. Generally, a server selects only one network interface to send packets, only selecting another if there is a network or traffic transmission failure.
- 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 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 solve the problem, configure MAC address-triggered ARP entry update on the switches. This function enables a switch to update the corresponding ARP entry when the outbound interface in a MAC address entry changes.
