Users Guide

Next Cand_RP_advertisement in 00:00:09
RP: 10.1.2.8(loopback10)
To view RP-mapping details:
OS10# show ip pim rp mapping
Group(s) : 225.1.1.0/24
RP : 10.1.2.8, v2
Info source: 10.1.1.8, via bootstrap, priority 23
expires: 00:01:04
Configure designated router priority
Multiple PIM-SM routers can connect to a single local area network (LAN) segment. One of these routers is elected as the
designated router (DR).
The DR is elected using hello messages. Each PIM router learns about its neighbors by periodically sending a hello message from
each PIM-enabled interface. Hello messages contain the interface IP address from where it is sent and a DR priority value. The
router with the highest priority value becomes the DR. If the priority value is the same for two routers, the router with the
highest IP address is the DR. By default, the DR priority value is 1, so the IP address determines the DR.
To configure DR priority, use the following command:
OS10# configure terminal
OS10(config)# interface vlan 100
OS10(conf-if-vl-100)# ip pim dr-priority 200
Update RP mapping cache with new RP configuration
If you make changes to the RP configuration, the system continues to use the old RP until the next BSR advertisement arrives.
To clear the group-to-RP mapping entries from the RP mapping cache, use the clear ip pim rp-mapping command. This
command removes only the group-to-RP mapping entries learned through the BSR updates. The system downloads the group-
to-RP mapping entries at the next BSR update.
PIM join filters
The PIM join filter allows you to permit or deny PIM Join/Prune messages on an interface using an extended IP access list.
PIM router propagates (*, G) and (S,G) Join/Prune messages from its neighbors and creates multicast route to forward the
traffic. This process can lead to PIM state explosion and high memory consumption when large numbers of PIM Join/Prune
messages are forwarded to each router on the rendezvous point tree (RPT). Use PIM join filters to prevent the PIM-enabled
routers from creating a multicast state and to limit multicast traffic in the network.
When the join filter is applied on the downstream interface, the effect on the outgoing interface happens at the maximum of
Join/Prune-HoldTime value.
To configure join filter for IPv4 PIM-enabled interface, use the following command:
ip pim join-filter <acl-name>
Configuration notes
● Dell Technologies recommends not using the ip pim join-filter command on an interface between a source and the
RP router. Using this command in this scenario could cause problems with the PIM-SM source registration process resulting
in excessive traffic being sent to the CPU of both the RP and PIM DR of the source.
Excessive traffic generates when the join process from the RP back to the source is blocked due to a new source group
being permitted in the join-filter. This results in the new source becoming stuck in registering on the DR and the continuous
generation of UDP-encapsulated registration messages between the DR and RP routers which are sent to the CPU.
Multicast
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