UMN:CLI User Manual
V5808
446
• Join/prune
Join/prune messages are sent by routers towards upstream sources or RPs. Join
messages are sent to receive the multicast traffic by building shared trees (RPT) or
source trees (SPT). Prune messages are sent to prune established distribution trees
when there are no more interests in the traffic.
• Bootstrap
The bootstrap router (BSR) sends bootstrap messages to elect the Rendezvous Point
(RP), which contain a set of the information for each candidate RP (RP-set).
• Assert
Assert messages are used to resolve forwarding conflicts among routers.
• Candidate RP advertisement
Each candidate RP unicasts these messages containing its own information to the
BSR. The BSR then includes a set of that information in the bootstrap message.
9.3.2.1 PIM Mode
To enable PIM-SM on an interface, use the following command.
Enables PIM-SM on an interface.
Disables PIM-SM on an interface.
You can also enable PIM-SM as the passive mode. The passive mode operation is for
local members. The passive mode disables sending/receiving PIM packets on an
interface, allowing only IGMP mechanism to be active.
To enable PIM-SM passive mode on an interface, use the following command.
ip pim sparse-mode passive
Enables PIM-SM passive mode on an interface.
no ip pim sparse-mode passive
Disables PIM-SM passive mode on an interface.
9.3.2.2 DR Priority
In PIM-SM, the designated router (DR) is normally the first-hop router of receivers (hosts),
which is responsible to periodically send PIM join/prune messages toward the RP to
inform it of the host group membership.
When there are multiple routers on the same subnet, one of them must be selected to act
as the DR. To elect the DR, each PIM router examines PIM hello messages received from
other neighbor PIM routers and compares its DR priority in those from neighbors. The
router with the highest priority then is elected as the DR. In case of more than one router
with the same highest priority value, the one with the higher IP address is elected. If no
PIM hello message is received from the DR for a certain period of time, another DR
election is held.
In PIM-DM, however, the DR only plays a role of the alternative IGMP querier using this
DR election when multiple routers exist with IGMPv1, since IGMPv1 does not define any
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