R2511-HP MSR Router Series High Availability Configuration Guide(V5)

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 have 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 the virtual MAC

address 000f-e2ff-0011.

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.

4. 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. 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—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. The new AVF stops forwarding the

packets destined for the virtual MAC address corresponding to the failed AVF.

5. 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 role, 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

NQA and 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 specific value. Then, the VF

with a higher priority becomes the AVF and forwards packets.

The VF tracking function can also work on an LVF to monitor its corresponding AVF on another

router. When the AVF fails, the LVF immediately takes over the AVF to ensure uninterrupted

network communications.

Packet types

VRRP standard mode defines only VRRP advertisement. Only the master in a VRRP group periodically

sends VRRP advertisements, and the backups do not send VRRP advertisements.

VRRP load balancing mode defines the following types of packets:

• Advertisement—VRRP advertises VRRP group state and information about the VF that is in the active

state. Both the master and the backups periodically send VRRP advertisements.