Hello messages, Track ports and track priority – Brocade TurboIron 24X Series Configuration Guide User Manual
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Brocade TurboIron 24X Series Configuration Guide
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Overview
Hello messages
VRRP routers use Hello messages for negotiation to determine the Master router. VRRP 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 uses the Hello interval you configure for the Backup 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 Backups
to select a new Master router. The Backup router with the highest priority becomes the new Master.
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 that is
acting as Master and the Owner therefore does not resume its position as Master. For more
information about track ports, refer to
“Track ports and track priority”
By default, if a Backup is acting as the Master, and the Master is still unavailable, another Backup
can “preempt” the Backup that is acting as the Master. This can occur if the new Backup has a
higher priority than the Backup who is acting as Master. You can disable this behavior if you want.
When you disable preemption, a Backup router that has a higher priority than the router who is
currently acting as Master does not preempt the new Master by initiating a new Master negotiation.
Refer to
NOTE
Regardless of the setting for the preempt parameter, the Owner always becomes the Master again
when it comes back online.
Track ports and track priority
The VRRP enhances the protocol by giving a VRRP router the capability to monitor the state of the
interfaces on the other end of the route path through the router. For example, in
page 864, interface e 6 on Switch 1 owns the IP address to which Host1 directs route traffic on its
default gateway. The exit path for this traffic is through Router1 e 4 interface.
Suppose interface e 4 goes down. Even if interface e 6 is still up, Host1 is nonetheless cut off from
other networks. In conventional VRRP, Switch 1 would continue to be the Master router despite the
unavailability of the exit interface for the path the router is supporting. However, if you configure
interface e 6 to track the state of interface e 4, if e 4 goes down, interface e 6 responds by
changing Switch 1 VRRP priority to the value of the track priority. In the configuration shown in
on page 864, Switch 1 priority changes from 255 to 20. One of the parameters
contained in the Hello messages the Master router sends to its Backups is the Master router
priority. If the track port feature results in a change in the Master router priority, the Backup routers
quickly become aware of the change and initiate a negotiation for Master router.
on page 864, the track priority results in Switch 1 VRRP priority becoming lower than
Switch 2 VRRP priority. As a result, when Switch 2 learns that it now has a higher priority than
Switch 1, Switch 2 initiates negotiation for Master router and becomes the new Master router, thus
providing an open path for Host1 traffic. To take advantage of the track port feature, make sure