H3C Technologies H3C S6800 Series Switches - Manual (Page 32)

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Figure 14 shows the VF table on each router in the VRRP group and how the VFs back up one another.
The master, Router A, assigns virtual MAC addresses 000f-e2ff-0011, 000f-e2ff-0012, and
000f-e2ff-0013 to itself, Router B, and Router C; and each router creates VF 1, VF 2, and VF 3,
respectively, for the virtual MAC addresses. The VFs for the same virtual MAC address on different routers
back up one another. For example, the VF 1 instances on Router A, Router B, and Router C back up one
another.
• The VF 1 instance on Router A (the VF 1 owner) has priority 255 and acts as the AVF to forward
packets sent to virtual MAC address 000f-e2ff-0011.
• The VF 1 instances on Router B and Router C have a priority of 255/(1 + 1), or 127. Because their
priorities are lower than the priority of the VF 1 instance on Router A, they act as LVFs to listen to the
state of the VF 1 instance on Router A.
• When the VF 1 instance on Router A fails, the VF 1 instances on Router B and Router C elect the one
with higher priority as the new AVF to forward packets destined for virtual MAC address
000f-e2ff-0011. If the two LVFs' priorities are the same, the LVF with a greater device MAC address
becomes the new AVF.
A VF always operates in preemptive mode. When an LVF finds its priority value higher than the one
advertised by the AVF, the LVF declares itself as the AVF.
VF timers
When the AVF on a router fails, the new AVF on another router creates a redirect timer and a timeout
timer for the failed AVF, as follows:
• Redirect timer—Before this timer expires, the master still uses the virtual MAC address
corresponding to the failed AVF to respond to ARP/ND requests from hosts, and the VF owner can
share traffic load if the VF owner resumes normal operation within this time. When this timer expires,
the master stops using the virtual MAC address corresponding to the failed AVF to respond to
ARP/ND requests from hosts.
• Timeout timer—The duration after which the new AVF takes over responsibilities of the failed VF
owner. Before this timer expires, all routers in the VRRP group keep the VFs that correspond to the
failed AVF, and the new AVF forwards packets destined for the virtual MAC address of the failed
AVF. When this timer expires, all routers in the VRRP group remove the VFs that correspond to the
failed AVF, including the new AVF. Packets destined for the virtual MAC address of the failed AVF
are not forwarded any longer.
Protocols and standards
• RFC 3768, Virtual Router Redundancy Protocol (VRRP)
• RFC 5798, Virtual Router Redundancy Protocol (VRRP) Version 3 for IPv4 and IPv6
Configuring IPv4 VRRP
This section describes how to configure IPv4 VRRP.