Brocade Communications Systems Layer 3 Routing Configuration ICX 6650 - Manual (Page 433)

Brocade ICX 6650 Layer 3 Routing Configuration Guide 415
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VRRP and VRRP-E overview
Master negotiation
The routers within a VRID use the VRRP priority values associated with each router to determine
which router becomes the Master. When you configure the VRID on a router interface, you specify
whether the router is the Owner of the IP addresses you plan to associate with the VRID or a
Backup router. If you indicate that the router is the Owner of the IP addresses, the software
automatically sets the router VRRP priority for the VRID to 255, the highest VRRP priority. The
router with the highest priority becomes the Master.
Backup routers can have a priority from 3 through 254, which you assign when you configure the
VRID on the Backup router interfaces. The default VRRP priority for Backup routers is 100.
Because the router that owns the IP addresses associated with the VRID always has the highest
priority, when all the routers in the virtual router are operating normally, the negotiation process
results in the Owner of the VRID IP addresses becoming the Master router. Thus, the VRRP
negotiation results in the normal case, in which the host’s path to the default route is to the router
that owns the interface for that route.
Hello messages
Virtual routers use Hello messages for negotiation to determine the Master router. Virtual routers
send Hello messages to IP Multicast address 224.0.0.18. The frequency with which the Master
sends Hello messages is the Hello interval. Only the Master sends Hello messages. However, a
Backup router uses the Hello interval you configure for the Backup router if it becomes the Master.
The Backup routers wait for a period of time called the dead interval for a Hello message from the
Master. If a Backup router does not receive a Hello message by the time the dead interval expires,
the Backup router assumes that the Master router is dead and negotiates with the other Backup
routers to select a new Master router. The Backup router with the highest priority becomes the new
Master.
Master and Owner backup routers
If the Owner becomes unavailable, but then comes back online, the Owner again becomes the
Master router. The Owner becomes the Master router again because it has the highest priority.
The Owner always becomes the Master again when the Owner comes back online.
NOTE
If you configure a track port on the Owner and the track port is down, the Owner priority is changed
to the track priority. In this case, the Owner does not have a higher priority than the Backup router
that is acting as the Master router and the Owner therefore does not resume its position as the
Master router. For more information about track ports, refer to
“Track ports and track priority” on
page 416.
By default, if a Backup is acting as the Master, and the original Master is still unavailable, another
Backup can “preempt” the Backup that is acting as the Master. This can occur if the new Backup
router has a higher priority than the Backup router that is acting as the Master. You can disable
this behavior. When you disable preemption, a Backup router that has a higher priority than the
router that is currently acting as the Master does not preempt the new Master by initiating a new
Master negotiation. Refer to
“Backup preempt configuration” on page 440.