Users Guide

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.
● Do not to configure a PIM join-filter on a source connected interface (IIF) on first hop router (FHR) node. Applying PIM
join-filter with the rule, deny ip any any might block creation of the S,G entries.
● When you configure a join filter, it applies for both incoming and outgoing joins. There is no option to specify in or out
parameters while configuring a join filter.
Configure PIM join filters
Before you configure a PIM join filter, enable multicast routing globally and establish PIM neighborship between routers. For
more information, see the ip multicast-routing command.
To configure a join filter that applies an ACL to the interface:
1. Configure an ACL in CONFIGURATION mode. You can specify the ACL name up to 140 characters.
OS10# configure terminal
OS10(config)# ip access-list pim_joinfilter
OS10(config-ipv4-acl)# permit ip 10.10.10.0/24 226.1.1.0/24
OS10(config-ipv4-acl)# permit ip any 225.1.1.0/24
PIM join filter uses both source and group information from the access-list for filtering joins. In this example, the first
permit ip command is used to filter Join messages for an (S,G) pair. The second permit ip command is used to filter
all join messages for a Group (G) irrespective of the sources.
2. Configure an Ethernet interface. This command enables INTERFACE configuration mode.
OS10(config)# interface ethernet 1/1/1
3. Configure a join filter that applies the previously created ACL (pim_joinfilter) on the PIM interface.
OS10(conf-if-eth1/1/1)# ip pim join-filter pim_joinfilter
1074
Multicast