An active virtual forwarder (AVF) is a GLBP router role that actively forwards traffic for a shared gateway. Each AVF receives a unique virtual MAC address, allowing multiple routers to serve hosts in one subnet. section 19.2.3
GLBP elects an Active Virtual Gateway (AVG), which assigns up to four AVFs. The AVG answers ARP requests with an AVF’s virtual MAC address in round-robin order, distributing hosts across the forwarders while they use one virtual IP address. section 19.2.3
Two-router GLBP LAN
In a 10.0.0.0/24 LAN, R1 and R2 can act as AVFs. The AVG returns R1’s virtual MAC to some hosts and R2’s to others, so traffic is load-balanced within the same subnet. AVF 1 in group 1 uses 0007.b400.0101. section 19.2.3
Figure 19.6 GLBP enables load balancing among hosts in the same subnet. Half of the hosts in 10.0.0.0/24 use one AVF (R1) as their default gateway, and the other half use the other AVF (R2). Each AVF has a unique virtual MAC address.
Use the figure to visualize how one virtual IP and multiple AVF virtual MAC addresses distribute hosts across routers. section 19.2.3
