Configuring HSRP between Gatekeepers
Cisco gatekeepers run a standard version IOS with the H.323/MCM feature set.
Thus, they have many common IOS capabilities, including HSRP. As with any
routing implementation, HSRP is an excellent way to provide redundancy
between routers.
In this scenario, you will probably want to configure the endpoints (such as
CallManagers) and other gatekeepers to register with a specific IP address (which
will be required anyway unless you plan to implement the multicast solution). In
this case, configure your endpoints and other gatekeepers to register with the
HSRP address.This way, regardless of which router is the active gatekeeper, all
devices will be able to successfully register with the gatekeeper.
You should configure the gatekeepers to use the HSRP address as their local
RAS address for all zones.You can do this by using the zone local command
and specifying at the end of the command a local IP address that the gatekeeper
should use.This will force the gatekeepers to use that address for all communication
with endpoints and gateways in that zone.
In the event of a failure where the back-up gatekeeper becomes active,
failover will not be transparent.The two HSRP gatekeepers do not share state
tables, thus all endpoints and other gatekeepers will need to re-register with the
newly active gatekeeper.This should only cause a minor service disruption.
In order to assure full functionality in the event of a failover, maintain exact
gatekeeper configurations on both devices.When changes are made, be diligent
to make identical changes on the backup router.
You can implement HSRP with two dedicated routers, though often this is
not economically practical.A more feasible approach might be to deploy the primary
gatekeeper with either a dedicated router or a router that does not have a
heavy load (such as a router that connects to a test environment, for example).
The backup gatekeeper can be an existing router that performs several other
functions. Although overall performance may be degraded in a failure scenario,
this will likely occur very infrequently. In this case, you may want to configure
the primary gatekeeper with not only a higher HSRP priority but also with
HSRP preempt so that it may resume the gatekeeper function as soon as it has
recovered. Use Table 5.3 to gauge the approximate size of the router required for
both your primary and HSRP standby router.