User's Manual

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switch_config_v9#ip pim-sm nbr-filter nbr_permit
switch_config_v9#exit
switch_config#ip access-list standard nbr_permit
switch_config_std_nacl#permit 172.20.21.174 255.255.255.0
Configuration result: enable hello packets from segment 172.20.21.0/24 and set up neighbor relation.
R172_config_std_nacl#show ip pim-s nei
PIM-SMv2 Neighbor Table
Neighbor Interface Uptime/Expires DR
Address Prior
172.20.21.173 v9 00:15:24/00:01:30 1(DR)
Change the configuration as follows and the interface v9 only enables hello packets from
172.20.21.174.
S172_config_std_nacl#permit 172.20.21.174 255.255.255.255
The debug information is as follows:
2004-1-1 00:16:26 PIM-SM: rcvd hello from 172.20.21.173, filter by acl
The former established neighbor will be aged gradually until timeout:
S172#show ip pim-s nei
PIM-SMv2 Neighbor Table
Neighbor Interface Uptime/Expires DR
Address Prior
172.20.21.173 v9 00:17:21/00:00:03 1(DR)
75.2.4 DR Election
DR election is to select DR for the router segment by comparing the priority and IP address in the Hello
packets of each router.
The role of DR plays:
1. For response on the host IGMP(v1) information, if the host connects two or more PIM-SM
routers directly by the Ethernet, only DR informs these information and forwards packets (*,g)
join. If DR and assert winner on the receiver end confronts, the former prevails.
2. DR on the multicast source generates original registration packets and register to RP.
If a new neighbor is found, DR is responsible for forwarding the local memorized BSM packets.
If the locak tries to become DR, enhance the local DR priority and IP address value in condition of the
same DR priority.
Steps for configuring DR priority:
 Configures main ip address on the interface;
 Port protocol up;
 Configure pim-sm on the interface;
 Configure ip pim-sm dr-pri ** on the interface;