Defining supported multicast groups

An RP in the default candidate configuration supports the entire range of possible multicast groups. This range is expressed as a multicast address and mask, where the mask defines whether the address is for a single address or a range of contiguous addresses:

Multicast address

Mask

Address range

224.0.0.0

240.0.0.0

224.0.0.0 - 239.255.255.255

An alternate way to express the above (default) address and mask is:

224.0.0.0/4

In non-default candidate configurations, an RP allows up to four ranges of contiguous multicast groups, and/or individual multicast groups, or both. For example:

RP candidate configuration

Supported range of multicast groups

235.0.240.0/12

235.0.240.1 — 235.0.255.255

235.0.0.1/28

235.0.0.1 — 235.0.0.15

235.0.0.128/32

235.0.0.128 only

235.0.0.77/32

235.0.0.77 only

NOTE:

If a given multicast group is excluded from all RPs in a given domain, then that group will not be available to the multicast receivers connected in the domain.

For more on this topic, see Configuring C-RPs on PIM-SM routers.