User Manual
UMN:CLI
V5824G
373
9.3.2.1
PIM Mode
To enable PIM-SM on an interface, use the following command.
Command
Mode
Description
ip pim sparse-mode
Interface
Enables PIM-SM on an interface.
no ip pim sparse-mode
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.
Command
Mode
Description
ip pim sparse-mode
passive
Interface
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
IGMP querier election process.
To specify the DR priority on an interface, use the following command.
Command
Mode
Description
ip pim dr-priority
<
0-4294967294>
Interface
Specifies the DR priority on an interface.
0-4294967294: priority value (default: 1)
no ip pim dr-priority
<
0-4294967294>
Deletes the specified DR priority.
no ip pim dr-priority
The DR and the IGMP querier may be different routers in IGMPv2, while those are
typically the same router in IGMPv1. In IGMPv2, the DR is the router with the highest IP
address on the subnet, whereas the IGMP querier is the router with the lowest IP address.
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