N o t e s
Redundant Group Coverage Provides Fault-Tolerance. If a C-RP
elected to support a particular multicast group or range of groups becomes
unavailable, the router will be excluded from the RP-set. If the multicast group
configuration of one or more other C-RPs overlaps the configuration in the
failed RP, then another C-RP will be elected to support the multicast group(s)
formerly relying on the failed RP.
Static Rendezvous Point (Static-RP)
General Application. Like C-RPs, static-RPs control multicast forwarding
of specific multicast groups or ranges of contiguous groups. However, static-
RPs are not dynamically learned, and increase the configuration and monitor
ing effort needed to maintain them. As a result static-RPs are not generally
recommended for use except where one of the following conditions applies:
It is desirable to designate a specific router interface as a backup RP for
Specific multicast groups are expected, and a static-RP would help to
avoid overloading a given RP with a high volume of multicast traffic.
A C-RP for the same group(s) is less reliable than another RP that would
not normally be elected to support the group(s).
tighter traffic control or a higher priority is desired for specific multicast
While use of C-RPs and a BSR enable a dynamic selection of RPs for the
multicast group traffic in a network, using static-RPs involves manually
configuring all routers in the domain to be aware of each static RP. This can
increase the possibility of multicast traffic failure due to misconfigurations
within the PIM-SM domain. Also, because a BSR does not administer static-
RPs, troubleshooting PIM-SM traffic problems can become more complex.
For these reasons, use of static-RPs should be limited to applications where
no viable alternatives exist, or where the network is stable and requires
configuring and maintaining only a few routers.
If a static-RP operating as the primary RP for a multicast group fails, and the
PIM-SM configuration in the domain does not include a (secondary) dynamic
RP (C-RP) backup to the static-RP, then new multicast groups assigned to the
static-RP will not be available to multicast receivers in the domain. Also, if a
static-RP fails, support for existing groups routed through SPTs that exclude
the failed router will continue, but any existing flows routed through the RPT
PIM-SM (Sparse Mode)
PIM-SM Operation and Router Types