Protocols And Standards - HPE FlexFabric 5700 Series Configuration Manual

Figure 36 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.
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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.
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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.
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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:
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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. 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.
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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. 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.
VF tracking
An AVF forwards packets destined for the MAC address of the AVF. If the upstream link of the AVF
fails but no LVF takes over the AVF role, the hosts on the subnet that use the MAC address of the
AVF as their gateway MAC address cannot access the external network.
The VF tracking function can solve this problem. You can use NQA or BFD to monitor the upstream
link state of the VF owner, and establish the collaboration between the VFs and NQA or BFD through
the tracking function. When the upstream link fails, the state of the track entry changes to Negative,
and the weights of the VFs (including the AVF) on the router decrease by a specified value. The
corresponding LVF with a higher priority on another router 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 to ensure uninterrupted network
communications.

Protocols and standards

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RFC 3768, Virtual Router Redundancy Protocol (VRRP)
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RFC 5798, Virtual Router Redundancy Protocol (VRRP) Version 3 for IPv4 and IPv6
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