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Multicast IGMP Snooping and PIM Design and Implementation

date_range 18-Apr-23

Use this design to configure Internet Group Management Protocol (IGMP) and Protocol Independent Multicast (PIM) in your fabric to improve multicast replication. IGMP snooping preserves bandwidth because multicast traffic is forwarded only on interfaces where there are IGMP listeners. For instance, every leaf device does not need to receive every instance of multicast traffic.

For an overview of multicast, see Multicast Optimizations.

In this design, we are using an external PIM gateway, which extends multicast beyond the data center, and is useful in DCI implementations.

The next sections show how to configure and verify multicast.

Configuring IGMP Snooping

In this design, we are using IGMP snooping to constrain multicast traffic in a broadcast domain to interested receivers and multicast devices.

To configure IGMP snooping:

Configure IGMP snooping on all VXLAN enabled VLANs on the leafs. The current implementation does not support IGMP snooping on selected VXLAN enabled VLANs.

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set protocols igmp-snooping vlan BD-3 proxy
set vlans BD-3 vlan-id 3
set vlans BD-3 vxlan vni 100003

Verifying IGMP Snooping

Enter the following CLI commands to verify IGMP snooping:

Verify the local IGMP snooping state on the leaf.

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user@leaf-2> show igmp snooping membership vlan BD-3    
Instance: default-switch

Vlan: BD-3

Learning-Domain: default
Interface: ae11.0, Groups: 2
    Group: 225.0.1.1
        Group mode: Exclude
        Source: 0.0.0.0
        Last reported by: 10.0.3.7
        Group timeout:     215 Type: Dynamic
    Group: 225.0.1.2
        Group mode: Exclude
        Source: 0.0.0.0
        Last reported by: 10.0.3.7
        Group timeout:     207 Type: Dynamic

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user@leaf-2> show evpn igmp-snooping database l2-domain-id 100003
Instance: default-switch
    VN Identifier: 100003
        Group IP: 225.0.1.1, Source IP: 0.0.0.0, Access OIF Count: 1
        Group IP: 225.0.1.2, Source IP: 0.0.0.0, Access OIF Count: 1

Verify that the leaf is advertising the EVPN Type 7 route where IGMP is snooped.

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user@leaf-2> show route table __default_evpn__.evpn.0 match-prefix 7:*100003*225.0.1.[12]*
__default_evpn__.evpn.0: 215 destinations, 318 routes (215 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

7:192.168.1.4:10::99080706050403::100003::225.0.1.1::192.168.1.4/600               
                   *[EVPN/170] 04:55:32
                       Indirect
7:192.168.1.4:10::99080706050403::100003::225.0.1.2::192.168.1.4/600               
                   *[EVPN/170] 04:55:30
                       Indirect

Verify that the leaf and its multihomed ESI peer device are both advertising the EVPN Type 6 route for the multicast group.

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user@leaf-2> show route table default-switch.evpn.0 match-prefix 6:*100003*225.0.1.[12]*
default-switch.evpn.0: 100334 destinations, 198153 routes (100334 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

6:192.168.1.3:10::100003::225.0.1.1::192.168.1.3/520               
                   *[BGP/170] 04:55:09, localpref 100, from 192.168.0.4
                      AS path: I, validation-state: unverified
                    >  to 172.16.4.1 via ae1.0
                       to 172.16.4.3 via ae2.0
                    [BGP/170] 04:55:11, localpref 100, from 192.168.0.5
                      AS path: I, validation-state: unverified
                    >  to 172.16.4.1 via ae1.0
                       to 172.16.4.3 via ae2.0
6:192.168.1.3:10::100003::225.0.1.2::192.168.1.3/520               
                   *[BGP/170] 04:55:07, localpref 100, from 192.168.0.4
                      AS path: I, validation-state: unverified
                    >  to 172.16.4.1 via ae1.0
                       to 172.16.4.3 via ae2.0
                    [BGP/170] 04:55:10, localpref 100, from 192.168.0.5
                      AS path: I, validation-state: unverified
                    >  to 172.16.4.1 via ae1.0
                       to 172.16.4.3 via ae2.0
6:192.168.1.4:10::100003::225.0.1.1::192.168.1.4/520               
                   *[EVPN/170] 04:56:16
                       Indirect
6:192.168.1.4:10::100003::225.0.1.2::192.168.1.4/520               
                   *[EVPN/170] 04:56:14
                       Indirect

Configuring PIM

To configure PIM:

To configure inter-VNI multicast routing at the spine, create a routing instance for a tenant (a leaf device) named VRF-1. Configure the following in the routing instance:

Add the IRB interfaces to the leaf devices.
Enable PIM and configure the local address for this spine as the rendezvous point (RP).
Enable PIM on the IRB interfaces.

Spine 1:

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set routing-instances VRF-1 instance-type vrf
set routing-instances VRF-1 interface irb.1
set routing-instances VRF-1 interface irb.2
set routing-instances VRF-1 interface irb.3
set routing-instances VRF-1 interface irb.4
set routing-instances VRF-1 interface lo0.10
set routing-instances VRF-1 route-distinguisher 192.186.0.2:1
set routing-instances VRF-1 vrf-target target:100:1
set routing-instances VRF-1 protocols pim rp local address 10.0.1.242
set routing-instances VRF-1 protocols pim interface irb.1 family inet
set routing-instances VRF-1 protocols pim interface irb.1 mode sparse-dense
set routing-instances VRF-1 protocols pim interface irb.2 family inet
set routing-instances VRF-1 protocols pim interface irb.2 mode sparse-dense
set routing-instances VRF-1 protocols pim interface irb.3 family inet
set routing-instances VRF-1 protocols pim interface irb.3 mode sparse-dense
set routing-instances VRF-1 protocols pim interface irb.4 family inet
set routing-instances VRF-1 protocols pim interface irb.4 mode sparse-dense

Configure multicast routing on another spine. Configure a corresponding VRF routing instance for the same tenant as in step 6.

Add the IRB interfaces toward the leaf devices.
Enable PIM and configure the RP address on spine 1 as the static RP.
Enable PIM on the IRB interfaces.

Spine 2:

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set routing-instances VRF-1 instance-type vrf
set routing-instances VRF-1 interface irb.1
set routing-instances VRF-1 interface irb.2
set routing-instances VRF-1 interface irb.3
set routing-instances VRF-1 interface irb.4
set routing-instances VRF-1 interface lo0.10
set routing-instances VRF-1 route-distinguisher 192.168.0.3:1
set routing-instances VRF-1 vrf-target target:100:1
set routing-instances VRF-1 protocols pim rp static address 10.0.1.242
set routing-instances VRF-1 protocols pim interface irb.1 family inet
set routing-instances VRF-1 protocols pim interface irb.1 mode sparse-dense
set routing-instances VRF-1 protocols pim interface irb.2 family inet
set routing-instances VRF-1 protocols pim interface irb.2 mode sparse-dense
set routing-instances VRF-1 protocols pim interface irb.3 family inet
set routing-instances VRF-1 protocols pim interface irb.3 mode sparse-dense
set routing-instances VRF-1 protocols pim interface irb.4 family inet
set routing-instances VRF-1 protocols pim interface irb.4 mode sparse-dense

Verifying PIM

Enter the following commands to verify PIM:

On spine 1, check the PIM control plane on the RP, and verify that:

PIM joins are created from Type 6 routes that are generated by leaf devices.
IGMP reports are coming from non-IGMP snooping capable leaf devices.

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user@spine-1> show pim join instance VRF-1 225.0.1.0/30 extensive
Instance: PIM.VRF-1 Family: INET
R = Rendezvous Point Tree, S = Sparse, W = Wildcard

Group: 225.0.1.1
    Source: *
    RP: 10.0.1.242
    Flags: sparse,rptree,wildcard
    Upstream interface: Local                 
    Upstream neighbor: Local
    Upstream state: Local RP
    Uptime: 15:18:24 
    Downstream neighbors:
        Interface: irb.3                  
            10.0.3.242 State: Join Flags: SRW  Timeout: Infinity
            Uptime: 15:17:51 Time since last Join: 15:17:51
        Interface: irb.2                  
            10.0.2.242 State: Join Flags: SRW  Timeout: Infinity
            Uptime: 14:51:29 Time since last Join: 14:51:29
        Interface: irb.1                  
            10.0.1.242 State: Join Flags: SRW  Timeout: Infinity
            Uptime: 05:31:09 Time since last Join: 05:31:09
            10.0.1.245 State: Join Flags: SRW Timeout: 199
            Uptime: 15:17:28 Time since last Join: 00:00:11
    Number of downstream interfaces: 3
    Number of downstream neighbors: 4

Group: 225.0.1.2
    Source: *
    RP: 10.0.1.242
    Flags: sparse,rptree,wildcard
    Upstream interface: Local                 
    Upstream neighbor: Local
    Upstream state: Local RP
    Uptime: 15:18:24 
    Downstream neighbors:
        Interface: irb.3                  
            10.0.3.242 State: Join Flags: SRW  Timeout: Infinity
            Uptime: 15:17:51 Time since last Join: 15:17:51
        Interface: irb.2                  
            10.0.2.242 State: Join Flags: SRW  Timeout: Infinity
            Uptime: 14:51:29 Time since last Join: 14:51:29
        Interface: irb.1                  
            10.0.1.242 State: Join Flags: SRW  Timeout: Infinity
            Uptime: 05:31:09 Time since last Join: 05:31:09
            10.0.1.245 State: Join Flags: SRW Timeout: 199
            Uptime: 15:17:28 Time since last Join: 00:00:11
    Number of downstream interfaces: 3
    Number of downstream neighbors: 4

On the spine that is configured as the PIM DR, verify the multicast forwarding state from the spine to the tenant VRF. To do so:

Enter show pim interfaces instance on all spines, and check the State column to see which IRB interface is a DR.

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user@spine-1> show pim interfaces instance VRF-1 
Stat = Status, V = Version, NbrCnt = Neighbor Count,
S = Sparse, D = Dense, B = Bidirectional,
DR = Designated Router, DDR = Dual DR, DistDR = Distributed DR,
P2P = Point-to-point link, P2MP = Point-to-Multipoint,
Active = Bidirectional is active, NotCap = Not Bidirectional Capable

Name               Stat Mode IP V State        NbrCnt JoinCnt(sg/*g) DR address
irb.1              Up   SD    4 2 DR,NotCap         3 2/100          10.0.1.245
irb.2              Up   SD    4 2 DR,NotCap         3 0/0            10.0.2.245
irb.3              Up   SD    4 2 DR,NotCap         3 0/0            10.0.3.245
irb.4              Up   SD    4 2 DR,NotCap         3 98/0           10.0.4.245
pime.32769         Up   S     4 2 P2P,NotCap        0 0/0
irb.1              Up   SD    6 2 DR,NotCap         2 0/0            fe80:db8:10:0:1::254
irb.2              Up   SD    6 2 DR,NotCap         2 0/0            fe80:db8:10:0:2::254
irb.3              Up   SD    6 2 DR,NotCap         2 0/0            fe80:db8:10:0:3::254
irb.4              Up   SD    6 2 DR,NotCap         2 0/0            fe80:db8:10:0:4::254

On the PIM DR, display the multicast forwarding state.

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user@spine-2> show multicast route extensive instance VRF-1 group 225.0.1.0/30 
Instance: VRF-1 Family: INET

Group: 225.0.1.1
    Source: 10.0.1.5/32
    Upstream interface: irb.1
    Downstream interface list: 
        irb.3 irb.2 
    Number of outgoing interfaces: 3
    Session description: Unknown
    Statistics: 69 kBps, 559 pps, 309165 packets
    Next-hop ID: 2109194
    Upstream protocol: PIM
    Route state: Active
    Forwarding state: Forwarding
    Cache lifetime/timeout: 360 seconds
    Wrong incoming interface notifications: 0
    Uptime: 00:09:13

Group: 225.0.1.2
    Source: 10.0.1.5/32
    Upstream interface: irb.1
    Downstream interface list: 
        irb.3 irb.2 
    Number of outgoing interfaces: 3
    Session description: Unknown
    Statistics: 68 kBps, 554 pps, 307024 packets
    Next-hop ID: 2109194
    Upstream protocol: PIM
    Route state: Active
    Forwarding state: Forwarding
    Cache lifetime/timeout: 360 seconds
    Wrong incoming interface notifications: 0
    Uptime: 00:09:13

Multicast — Feature Summary

Table 1 provides a history of the features described in this section and their support within this reference design.

Table 1: Multicast Feature Summary
Hardware	IGMPv2 Snooping	EVPN Type 6 SMET Routes	Inter-VNI Multicast with PIM Gateway	PIM to External Rendezvous Point (From Border)
QFX5100¹	Not supported	Not supported	Not supported	Not supported
QFX5110-32Q, QFX5110-48S	18.1R3-S3	18.4R2	Not supported	Not supported
QFX5120-48Y	18.4R2	18.4R2	Not supported	Not supported
QFX5120-32C	19.1R2	19.1R2	Not supported	Not supported
QFX5200-32C¹, QFX5200-48Y¹	Not supported	Not supported	Not supported	Not supported
QFX10002-36Q/72Q, QFX10008, QFX10016	18.1R3-S3	18.4R2	18.1R3-S3	17.3R3-S1
QFX10002-60C²	20.2R2	20.2R2	20.2R2	20.2R2
MX204; MX240, MX480, MX960 with MPC7E; MX10003;	Not supported	Not supported	Not supported	Not supported

¹Make sure that IGMP snooping is not enabled on these QFX switches. If IGMP snooping is inadvertently enabled, these switches might process EVPN Type 6 routes that are reflected to them.

²The QFX10002-60C switch supports multicast at a lower scale than the QFX10002-36Q/72Q switches.

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Data Center EVPN-VXLAN Fabric Architecture Guide

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Multicast IGMP Snooping and PIM Design and Implementation

Configuring IGMP Snooping

Verifying IGMP Snooping

Configuring PIM

Verifying PIM

Multicast — Feature Summary

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Multicast IGMP Snooping and PIM Design and Implementation

Configuring IGMP Snooping

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