Reference Guide

732 | PIM Source-Specific Mode
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Use PIM-SSM with IGMP version 2 Hosts
PIM-SSM requires receivers that support IGMP version 3. You can employ PIM-SSM even when
receivers support only IGMP version 1 or version 2 by translating (*,G) entries to (S,G) entries.
Translate (*,G) entries to (S,G) entries using the command
ip igmp ssm-map acl source from
CONFIGURATION mode. In a standard access list, specify the groups or the group ranges that you want
to map to a source. Then, specify the multicast source.
• When a SSM map is in place and FTOS cannot find any matching access lists for a group, it continues
to create (*,G) entries because there is an implicit deny for unspecified groups in the ACL.
• When you remove the mapping configuration, FTOS removes the corresponding (S,G) states that it
created and reestablishes the original (*,G) states.
• You may enter multiple
ssm-map commands for different access lists. You may also enter multiple
ssm-map commands for the same access list, as long as they use different source addresses.
• When an extended ACL is associated with this command, FTOS displays an error message. If you
apply an extended ACL before you create it, FTOS accepts the configuration, but when the ACL is
later defined, FTOS ignores the ACL and the stated mapping has no effect.
Display the source to which a group is mapped using the command
show ip igmp ssm-map [group], as
shown in the example below. If the
group option is used, the command displays the group-to-source
mapping even if the group is not currently in the IGMP group table. If you do not specify the
group option,
then the display is a list of groups currently in the IGMP group table that have a group-to-source mapping.
Display the list of sources mapped to a group currently in the IGMP group table using the command
show
ip igmp groups group detail, as shown in the example below.