H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 22)

14
Figure 9 shows the VF table on each router in the VRRP group and how the routers 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 for the
virtual MAC addresses, respectively. 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 the
packets sent to virtual MAC address 000f-e2ff-0011.
• The VF 1 instances on Router B and Router C has priority 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 the packets destined for virtual MAC address
000f-e2ff-0011.
NOTE:
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 newly elected AVF on another router creates a redirect timer and a
timeout timer for the failed AVF.
• Redirect Timer—Before this timer times out, the master still uses the virtual MAC address
corresponding to the failed AVF to respond to ARP/ND requests from the hosts, and the VF owner
can share traffic load if the VF owner resumes normal operation within this time. When this timer
times out, the master stops using the virtual MAC address corresponding to the failed AVF to
respond to ARP/ND requests from the hosts.
• Timeout Timer—The duration that the new AVF takes over the VF owner. Before this timer times out,
all the routers in the VRRP group keep the failed AVF, and the new AVF forwards the packets
destined for the virtual MAC address corresponding to the failed AVF. When this timer times out, all
the routers in the VRRP group remove the failed AVF, and the new AVF stops forwarding the packets
destined for the virtual MAC address corresponding to the failed AVF.
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 use the MAC address of the AVF as
their gateway MAC address cannot access the external network.
This problem can be solved by 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 entry changes to negative and the weight of the
VF decreases by a specified value. Then, the VF with a higher priority becomes the AVF and forwards
packets.
Packet types
VRRP standard protocol mode defines only VRRP advertisement. Only the master in a VRRP group
periodically sends VRRP advertisements, and the backups do not send VRRP advertisements.