Avaya 8800 Planning And Engineering, Network Design page 207

Figure 97: RP failover with default unicast routes
Because failover is determined by unicast routing behavior, carefully consider the unicast routing
design, as well as the IP address you select for the RP. Static RP failover performance depends on
the convergence time of the unicast routing protocol. For quick convergence, Avaya recommends
that you use a link state protocol, such as OSPF. For example, if you are using RIP as the routing
protocol, an RP failure may take minutes to detect. Depending on the application, this situation can
be unacceptable.
Static RP failover time does not affect routers that have already switched over to the SPT; failover
time only affects newly-joining routers.
Specific route for static RP
With static RP enabled, the Avaya Ethernet Routing Switch 8800/8600 detects RP failure based on
IGP convergence and, more specifically, on the removal of the route to the RP from the routing
table. With the route to the failed RP removed, the Avaya Ethernet Routing Switch 8800/8600 can
fail over to an alternate static RP.
If a default route is injected into the routing table, that default route still appears as an active route to
the failed RP. Therefore, in this case, the switch does not fail over to the alternate RP.
A similar situation exists with SMLT-based configurations, where an internal-only default static route
is used during IST failover and recovery. In this case, the internal default route appears as an active
route to the failed RP, and therefore does not failover to the alternate RP.
To resolve the preceding situations, you can configure the lookup for static RP to be chosen from
the specific route rather than the best route. In this case, when the route to the active RP fails, the
switch no longer interprets the default route as a valid route for RP purposes, and therefore fails
over to the alternate RP.
Avaya recommends that you always enable the specific route option for any SMLT/RSMLT cluster
running PIM-SM with static RPs because of the implementation of the internal-only default static
route on the IST.
June 2016
Protocol Independent Multicast-Sparse Mode guidelines
Planning and Engineering — Network Design
Comments on this document? infodev@avaya.com
207