PIM

PIM – Protocol Independent Multicast

pimd supports pim-sm as well as igmp v2 and v3. pim is vrf aware and can work within the context of vrf’s in order to do S,G mrouting. Additionally PIM can be used in the EVPN underlay network for optimizing forwarding of overlay BUM traffic.

Starting and Stopping pimd

The default configuration file name of pimd’s is pimd.conf. When invoked pimd searches directory /etc/frr. If pimd.conf is not there then next search current directory.

pimd requires zebra for proper operation. Additionally pimd depends on routing properly setup and working in the network that it is working on.

# zebra -d
# pimd -d

Please note that zebra must be invoked before pimd.

To stop pimd please use:

kill `cat /var/run/pimd.pid`

Certain signals have special meanings to pimd.

Signal Meaning
SIGUSR1 Rotate the pimd logfile
SIGINT SIGTERM pimd sweeps all installed PIM mroutes then terminates gracefully.

pimd invocation options. Common options that can be specified (Common Invocation Options).

ip pim rp A.B.C.D A.B.C.D/M

In order to use pim, it is necessary to configure a RP for join messages to be sent to. Currently the only methodology to do this is via static rp commands. All routers in the pim network must agree on these values. The first ip address is the RP’s address and the second value is the matching prefix of group ranges covered. This command is vrf aware, to configure for a vrf, enter the vrf submode.

ip pim spt-switchover infinity-and-beyond

On the last hop router if it is desired to not switch over to the SPT tree. Configure this command. This command is vrf aware, to configure for a vrf, enter the vrf submode.

ip pim ecmp

If pim has the a choice of ECMP nexthops for a particular RPF, pim will cause S,G flows to be spread out amongst the nexthops. If this command is not specified then the first nexthop found will be used. This command is vrf aware, to configure for a vrf, enter the vrf submode.

ip pim ecmp rebalance

If pim is using ECMP and an interface goes down, cause pim to rebalance all S,G flows across the remaining nexthops. If this command is not configured pim only modifies those S,G flows that were using the interface that went down. This command is vrf aware, to configure for a vrf, enter the vrf submode.

ip pim join-prune-interval (60-600)

Modify the join/prune interval that pim uses to the new value. Time is specified in seconds. This command is vrf aware, to configure for a vrf, enter the vrf submode.

ip pim keep-alive-timer (31-60000)

Modify the time out value for a S,G flow from 31-60000 seconds. 31 seconds is chosen for a lower bound because some hardware platforms cannot see data flowing in better than 30 second chunks. This command is vrf aware, to configure for a vrf, enter the vrf submode.

ip pim packets (1-100)

When processing packets from a neighbor process the number of packets incoming at one time before moving on to the next task. The default value is 3 packets. This command is only useful at scale when you can possibly have a large number of pim control packets flowing. This command is vrf aware, to configure for a vrf, enter the vrf submode.

ip pim register-suppress-time (5-60000)

Modify the time that pim will register suppress a FHR will send register notifications to the kernel. This command is vrf aware, to configure for a vrf, enter the vrf submode.

ip pim send-v6-secondary

When sending pim hello packets tell pim to send any v6 secondary addresses on the interface. This information is used to allow pim to use v6 nexthops in it’s decision for RPF lookup. This command is vrf aware, to configure for a vrf, enter the vrf submode.

ip pim ssm prefix-list WORD

Specify a range of group addresses via a prefix-list that forces pim to never do SM over. This command is vrf aware, to configure for a vrf, enter the vrf submode.

ip multicast rpf-lookup-mode WORD

Modify how PIM does RPF lookups in the zebra routing table. You can use these choices:

longer-prefix
Lookup the RPF in both tables using the longer prefix as a match
lower-distance
Lookup the RPF in both tables using the lower distance as a match
mrib-only
Lookup in the Multicast RIB only
mrib-then-urib
Lookup in the Multicast RIB then the Unicast Rib, returning first found. This is the default value for lookup if this command is not entered
urib-only
Lookup in the Unicast Rib only.
ip igmp generate-query-once [version (2-3)]

Generate IGMP query (v2/v3) on user requirement. This will not depend on the existing IGMP general query timer.If no version is provided in the cli, it will be considered as default v2 query.This is a hidden command.

PIM Interface Configuration

PIM interface commands allow you to configure an interface as either a Receiver or a interface that you would like to form pim neighbors on. If the interface is in a vrf, enter the interface command with the vrf keyword at the end.

ip pim bfd

Turns on BFD support for PIM for this interface.

ip pim bsm

Tell pim that we would like to use this interface to process bootstrap messages. This is enabled by default. ‘no’ form of this command is used to restrict bsm messages on this interface.

ip pim unicast-bsm

Tell pim that we would like to allow interface to process unicast bootstrap messages. This is enabled by default. ‘no’ form of this command is used to restrict processing of unicast bsm messages on this interface.

ip pim drpriority (1-4294967295)

Set the DR Priority for the interface. This command is useful to allow the user to influence what node becomes the DR for a lan segment.

ip pim hello (1-180) (1-180)

Set the pim hello and hold interval for a interface.

ip pim sm

Tell pim that we would like to use this interface to form pim neighbors over. Please note that this command does not enable the reception of IGMP reports on the interface. Refer to the next ip igmp command for IGMP management.

ip igmp

Tell pim to receive IGMP reports and Query on this interface. The default version is v3. This command is useful on a LHR.

ip igmp join A.B.C.D A.B.C.D

Join multicast source-group on an interface.

ip igmp query-interval (1-1800)

Set the IGMP query interval that PIM will use.

ip igmp query-max-response-time (10-250)

Set the IGMP query response timeout value. If an report is not returned in the specified time we will assume the S,G or *,G has timed out.

ip igmp version (2-3)

Set the IGMP version used on this interface. The default value is 3.

ip multicast boundary oil WORD

Set a pim multicast boundary, based upon the WORD prefix-list. If a pim join or IGMP report is received on this interface and the Group is denied by the prefix-list, PIM will ignore the join or report.

ip igmp last-member-query-count (1-7)

Set the IGMP last member query count. The default value is 2. ‘no’ form of this command is used to to configure back to the default value.

ip igmp last-member-query-interval (1-255)

Set the IGMP last member query interval in deciseconds. The default value is 10 deciseconds. ‘no’ form of this command is used to to configure back to the default value.

PIM Multicast RIB insertion:

In order to influence Multicast RPF lookup, it is possible to insert into zebra routes for the Multicast RIB. These routes are only used for RPF lookup and will not be used by zebra for insertion into the kernel or for normal rib processing. As such it is possible to create weird states with these commands. Use with caution. Most of the time this will not be necessary.

ip mroute A.B.C.D/M A.B.C.D (1-255)

Insert into the Multicast Rib Route A.B.C.D/M with specified nexthop. The distance can be specified as well if desired.

ip mroute A.B.C.D/M INTERFACE (1-255)

Insert into the Multicast Rib Route A.B.C.D/M using the specified INTERFACE. The distance can be specified as well if desired.

Show PIM Information

All PIM show commands are vrf aware and typically allow you to insert a specified vrf command if information is desired about a specific vrf. If no vrf is specified then the default vrf is assumed. Finally the special keyword ‘all’ allows you to look at all vrfs for the command. Naming a vrf ‘all’ will cause great confusion.

show ip igmp interface

Display IGMP interface information.

show ip igmp join

Display IGMP static join information.

show ip igmp groups

Display IGMP groups information.

show ip igmp groups retransmissions

Display IGMP group retransmission information.

show ip igmp sources

Display IGMP sources information.

show ip igmp sources retransmissions

Display IGMP source retransmission information.

show ip igmp statistics

Display IGMP statistics information.

show ip multicast

Display various information about the interfaces used in this pim instance.

show ip mroute [vrf NAME] [A.B.C.D [A.B.C.D]] [fill] [json]

Display information about installed into the kernel S,G mroutes. If one address is specified we assume it is the Group we are interested in displaying data on. If the second address is specified then it is Source Group. The keyword fill says to fill in all assumed data for test/data gathering purposes.

show ip mroute count

Display information about installed into the kernel S,G mroutes and in addition display data about packet flow for the mroutes.

show ip mroute summary

Display total number of S,G mroutes and number of S,G mroutes installed into the kernel.

show ip pim assert

Display information about asserts in the PIM system for S,G mroutes.

show ip pim assert-internal

Display internal assert state for S,G mroutes

show ip pim assert-metric

Display metric information about assert state for S,G mroutes

show ip pim assert-winner-metric

Display winner metric for assert state for S,G mroutes

show ip pim group-type

Display SSM group ranges.

show ip pim interface

Display information about interfaces PIM is using.

show ip pim join

Display information about PIM joins received. If one address is specified then we assume it is the Group we are interested in displaying data on. If the second address is specified then it is Source Group.

show ip pim local-membership

Display information about PIM interface local-membership.

show ip pim neighbor

Display information about PIM neighbors.

show ip pim nexthop

Display information about pim nexthops that are being used.

show ip pim nexthop-lookup

Display information about a S,G pair and how the RPF would be chosen. This is especially useful if there are ECMP’s available from the RPF lookup.

show ip pim rp-info

Display information about RP’s that are configured on this router.

show ip pim rpf

Display information about currently being used S,G’s and their RPF lookup information. Additionally display some statistics about what has been happening on the router.

show ip pim secondary

Display information about an interface and all the secondary addresses associated with it.

show ip pim state

Display information about known S,G’s and incoming interface as well as the OIL and how they were chosen.

show ip pim upstream

Display upstream information about a S,G mroute. Allow the user to specify sub Source and Groups that we are only interested in.

show ip pim upstream-join-desired

Display upstream information for S,G’s and if we desire to join the multicast tree

show ip pim upstream-rpf

Display upstream information for S,G’s and the RPF data associated with them.

show ip pim bsr

Display current bsr, its uptime and last received bsm age.

show ip pim bsrp-info

Display group-to-rp mappings received from E-BSR.

show ip pim bsm-database

Display all fragments ofstored bootstrap message in user readable format.

show ip rpf

Display the multicast RIB created in zebra.

mtrace A.B.C.D [A.B.C.D]

Display multicast traceroute towards source, optionally for particular group.

PIM Debug Commands

The debugging subsystem for PIM behaves in accordance with how FRR handles debugging. You can specify debugging at the enable CLI mode as well as the configure CLI mode. If you specify debug commands in the configuration cli mode, the debug commands can be persistent across restarts of the FRR pimd if the config was written out.

debug igmp

This turns on debugging for IGMP protocol activity.

debug mtrace

This turns on debugging for mtrace protocol activity.

debug mroute

This turns on debugging for PIM interaction with kernel MFC cache.

debug pim events

This turns on debugging for PIM system events. Especially timers.

debug pim nht

This turns on debugging for PIM nexthop tracking. It will display information about RPF lookups and information about when a nexthop changes.

debug pim packet-dump

This turns on an extraordinary amount of data. Each pim packet sent and received is dumped for debugging purposes. This should be considered a developer only command.

debug pim packets

This turns on information about packet generation for sending and about packet handling from a received packet.

debug pim trace

This traces pim code and how it is running.

debug pim bsm

This turns on debugging for BSR message processing.

debug pim zebra

This gathers data about events from zebra that come up through the ZAPI.

PIM Clear Commands

Clear commands reset various variables.

clear ip interfaces

Reset interfaces.

clear ip igmp interfaces

Reset IGMP interfaces.

clear ip mroute

Reset multicast routes.

clear ip mroute [vrf NAME] count

When this command is issued, reset the counts of data shown for packet count, byte count and wrong interface to 0 and start count up from this spot.

clear ip pim interfaces

Reset PIM interfaces.

clear ip pim oil

Rescan PIM OIL (output interface list).

PIM EVPN configuration

To use PIM in the underlay for overlay BUM forwarding associate a multicast group with the L2 VNI. The actual configuration is based on your distribution. Here is an ifupdown2 example:

auto vx-10100
iface vx-10100
    vxlan-id 10100
    bridge-access 100
    vxlan-local-tunnelip 27.0.0.11
    vxlan-mcastgrp 239.1.1.100

Note

PIM will see the vxlan-mcastgrp configuration and auto configure state to properly forward BUM traffic.

PIM also needs to be configured in the underlay to allow the BUM MDT to be setup. This is existing PIM configuration:

  • Enable pim on the underlay L3 interface via the “ip pim” command.
  • Configure RPs for the BUM multicast group range.
  • Ensure the PIM is enabled on the lo of the VTEPs and the RP.