PIM - Multicast Boundary

The multicast boundary feature, when used with a standard acl, can be used to filter (S,G) and (*,G) join messages to the RP as well as filter mcast traffic destined to a multicast group. Note it does not filter PIM register messages as these are sent as unicast messages from the PIM DR to the PIM RP.

Consider the following configuration

access-list 5 deny 232.0.0.0 7.255.255.255
access-list 5 permit 224.0.0.0 15.255.255.255

int fa0/0
ip multicast boundary 5 filter-autorp


This command will filter multicast traffic for the range 232.0.0.0/5. This includes any traffic in this range plus any ranges that overlap with this range.

The addition of the filter-autorp messages ensures the filtering is applied to rp announcements as well as multicast traffic.

For example the downstream switch SW2 was receiving announcements for the following groups.

SW2#s ip pim rp map
PIM Group-to-RP Mappings

Group(s) 224.0.0.0/5
RP 150.1.7.7 (?), v2v1
Info source: 150.1.1.1 (?), elected via Auto-RP
Uptime: 00:19:45, expires: 00:02:33
Group(s) 224.0.0.0/4
RP 150.1.9.9 (?), v2v1
Info source: 150.1.1.1 (?), elected via Auto-RP
Uptime: 00:19:15, expires: 00:01:34
Group(s) (-)224.50.50.50/32
RP 150.1.9.9 (?), v2v1
Info source: 150.1.1.1 (?), elected via Auto-RP
Uptime: 00:19:15, expires: 00:02:36
Group(s) 232.0.0.0/5
RP 150.1.9.9 (?), v2v1
Info source: 150.1.1.1 (?), elected via Auto-RP
Uptime: 00:19:15, expires: 00:01:37


After the multicast boundary statement wis applied to the upstream neighbor rp announcements for 232.0.0./5 and 224.0.0.0/4 are both removed.

SW2#s ip pim rp map
PIM Group-to-RP Mappings

Group(s) 224.0.0.0/5
RP 150.1.7.7 (?), v2v1
Info source: 150.1.1.1 (?), elected via Auto-RP
Uptime: 00:23:58, expires: 00:02:20
Group(s) (-)224.50.50.50/32
RP 150.1.9.9 (?), v2v1
Info source: 150.1.1.1 (?), elected via Auto-RP