R3204P16-HP Load Balancing Module High Availability Configuration Guide-6PW101

The priority of a VF decides the VF state. A VF with the highest priority is in the active state and is known

as the active virtual forwarder (AVF), which forwards packets; other VFs are in the listening state and are

known as the listening virtual forwarders (LVFs), which listen to the state of the AVF. The priority value of

a VF ranges from 0 to 255, where 255 is reserved for the VF owner.

The priority value of a VF is calculated based on its weight.

2. VF backup

If the weight of the VF owner is no less than the lower limit of failure, the priority of the VF owner is the

highest value 255. Therefore, the VF owner is the AVF and forwards packets destined to the MAC

address of the AVF. After receiving the advertisements sent by the AVF, other routers in the VRRP group

create their own VFs, which are in the listening state. Figure 7 illu

strates the VF information on each router

in the VRRP group.

Figure 7 VF information

LVFs listen the AVF. When the AVF fails, the LVFs elect a new AVF with the highest priority value among

the LVFs.

A VF always works in the preemption mode. When an LVF finds its priority higher than that in the

advertisement sent by the AVF, the LVF declares itself as the AVF.

3. VF tracking

The AVF forwards packets destined to the MAC address of the AVF. If the uplink of the AVF fails and no

LVF is notified to take over the AVF's work, hosts (on the LAN) that take the MAC address of the AVF as

their gateway MAC address cannot access the external network.

You can solve this problem through the VF tracking function. You can monitor the uplink state by using

network quality analyzer (NQA) and bidirectional forwarding detection (BFD), and establish the

collaboration between the VF and the NQA or between the VF and the BFD through the tracking function.

When the uplink fails, the state of the monitored Track object changes to negative and the weight of the

VF decreases by a specified value. After that, the VF with a higher priority becomes the AVF and

forwards packets.