PIM Snooping for IPv4 in EVPN-MPLS and PBB-EVPN Services

PIM Snooping for VPLS allows a VPLS PE router to build multicast states by snooping PIM protocol packets that are sent over the VPLS. The VPLS PE then forwards multicast traffic based on the multicast states. When all receivers in a VPLS are IP multicast routers running PIM, multicast forwarding in the VPLS is efficient when PIM snooping for VPLS is enabled.

PIM snooping for IPv4 is supported in EVPN-MPLS (for VPLS and R-VPLS) and PBB-EVPN I-VPLS (where BGP EVPN is running in the associated B-VPLS service) services. It is enabled using the following command (as IPv4 multicast is enabled by default):

configure service vpls <service-id> pim-snooping 

PIM snooping on SAPs and spoke SDPs operates in the same way as in a plain VPLS service. However, EVPN-MPLS/PBB-EVPN B-VPLS destinations are treated as a single PIM interface, specifically:

PIM snooping for IPv4 is supported in EVPN-MPLS services using P2MP LSPs and PBB-EVPN I-VPLS services with P2MP LSPs in the associated B-VPLS service. When PIM snooping is enabled with P2MP LSPs, at least one EVPN-MPLS multicast destination is required to be established to enable the processing of PIM messages by the system.

Multi-chassis synchronization (MCS) of PIM snooping for IPv4 state is supported for both SAPs and spoke SDPs which can be used with single-active multihoming. Care should be taken when using *.null to define the range for a QinQ virtual ES if the associated SAPs are also being synchronized by MCS, as there is no equivalent MCS sync-tag support to the *.null range.

PBB-EVPN services operate in a similar way to regular PBB services, specifically:

In EVPN-MPLS services, the individual EVPN-MPLS destinations appear in the MFIB but the information for each EVPN-MPLS destination entry is always identical, as shown below:

*A:PE# show service id 1 mfib
===============================================================================
Multicast FIB, Service 1
===============================================================================
Source Address  Group Address         Port Id                      Svc Id   Fwd
                                                                            Blk
-------------------------------------------------------------------------------
*               239.252.0.1           sap:1/1/9:1                  Local    Fwd
                                      eMpls:1.1.1.2:262141         Local    Fwd
                                      eMpls:1.1.1.3:262141         Local    Fwd
-------------------------------------------------------------------------------
Number of entries: 1
===============================================================================
*A:PE#

Similarly for the PIM neighbors:

*A:PE# show service id 1 pim-snooping neighbor
===============================================================================
PIM Snooping Neighbors ipv4
===============================================================================
Port Id                 Nbr DR Prty     Up Time       Expiry Time     Hold Time
  Nbr Address
-------------------------------------------------------------------------------
SAP:1/1/9:1             1               0d 00:08:17   0d 00:01:29     105
  10.0.0.1
EVPN-MPLS               1               0d 00:27:26   0d 00:01:19     105
  10.0.0.2
EVPN-MPLS               1               0d 00:27:26   0d 00:01:19     105
  10.0.0.3
-------------------------------------------------------------------------------
Neighbors : 3
===============================================================================
*A:PE#

A single EVPN-MPLS interface is shown in the outgoing interface, as can be seen in the following output:

*A:PE# show service id 1 pim-snooping group detail
===============================================================================
PIM Snooping Source Group ipv4
===============================================================================
Group Address      : 239.252.0.1
Source Address     : *
Up Time            : 0d 00:07:07
Up JP State        : Joined             Up JP Expiry       : 0d 00:00:37
Up JP Rpt          : Not Joined StarG   Up JP Rpt Override : 0d 00:00:00
RPF Neighbor       : 10.0.0.1
Incoming Intf      : SAP:1/1/9:1
Outgoing Intf List : EVPN-MPLS, SAP:1/1/9:1
Forwarded Packets  : 0                  Forwarded Octets   : 0
-------------------------------------------------------------------------------
Groups : 1
===============================================================================
*A:PE#

An example of the debug trace output for a join received on an EVPN-MPLS destination is shown below:

A:PE1# debug service id 1 pim-snooping packet jp
A:PE1#
32 2016/12/20 14:21:22.68 CET MINOR: DEBUG #2001 Base PIM[vpls 1 ]
"PIM[vpls 1 ]: Join/Prune
[000 02:16:02.460] PIM-RX ifId 1071394 ifName EVPN-MPLS 10.0.0.3 -> 224.0.0.13 
Length: 34
PIM Version: 2 Msg Type: Join/Prune Checksum: 0xd3eb
Upstream Nbr IP : 10.0.0.1 Resvd: 0x0, Num Groups 1, HoldTime 210
        Group: 239.252.0.1/32 Num Joined Srcs: 1, Num Pruned Srcs: 0
        Joined Srcs:
                10.0.0.1/32 Flag SWR  <*,G>

The equivalent output for PBB-EVPN services is similar to that above for EVPN-MPLS services, with the exception that the EVPN destinations are named ‟b-EVPN-MPLS”.