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 |
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.