HP 3500YL - Manual (Page 122)

PIM-SM (Sparse Mode)
PIM-SM Operation and Router Types
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
will fail.
Supporting a Static-RP as Primary . A static-RP can be configured to
operate as either a secondary or primary RP. With the primary option, a
dynamic (C-RP) backup is recommended. The precedence of a static-RP over
a dynamic RP is determined by the following static-RP configuration options:
• override enabled on the static-RP
• a group mask on the static-RP that equals or exceeds the group mask
on the C-RP for the same multicast group(s)
For override configuration information, refer to “Statically Configuring an RP
To Accept Multicast Traffic” on page 4-42.
Operating Rules for Static RPs.
■ Static-RPs can be configured on the same routers as C-RPs.
■ Where a C-RP and a static-RP are configured to support the same multicast
group(s), the C-RP takes precedence over the static-RP unless the static-
RP is configured to override the C-RP. (Refer to “Supporting a Static-RP
as Primary”, above.)
■ Any static-RP in a domain must be configured identically on all routers in
the domain. Otherwise, some DRs will not know of the static-RP and will
not forward the appropriate multicast traffic, and some routers will not
know where to send Joins for the groups supported by static-RP.
■ Up to four static-RP entries can be configured on a router. Each entry can
be for either a single multicast group or a range of contiguous groups.
■ Only one interface can be configured as the static RP for a given multicast
group or range of groups. For example, a properly configured PIM-SM
domain does not support configuring 10.10.10.1 and 10.20.10.1 to both
support a multicast group identified as 239.255.255.10.
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