Configuring Multicast Fabric VRFs


Note: This feature is supported only on  Dell S41xx-ON platforms.


The CLI commands to configure and verify distributed multicast forwarding with Multicast Fabric VRFs are described below:


CLI (network-admin@switch) > vrf-multicast-show

enable: yes


CLI (network-admin@switch) > vrf-multicast-modify


scope local|fabric  

Specify the scope - fabric or local

disable

Specify to disable flooding over tunnels in DM Forwarding

enable

Specify to enable flooding over tunnels in DM Forwarding



Enabling or disabling Multicast Fabric VRFs takes effect only after a reboot. For example, this command disables the feature:


CLI (network-admin@switch) > vrf-multicast-modify disable

System must be REBOOTED for this setting to take effect


A new command, vrf-mroute-show, can be used to show the L3 entries dynamically created to implement L3 multicast forwarding:


CLI (network-admin@switch) > vrf-mroute-show


srcip    group   vxlan  vlan vrid hw-group-id send-vlan ports  flags

------- --------- ----  ---- ---- ----------- --------- ----- ------

0.0.0.0 224.1.1.1 10501  501  0    0x200098a    0        none  Active

0.0.0.0 224.1.1.1 10501  501  1    0x200098a    506      1     Active


This command can be used to check the list of multicast destination groups, incoming VLANs, outgoing ports and egress VLANs.


The above output shows (*, 224.1.1.1, 501) with port 1 as outgoing port and 506 as egress VLAN. Note that this kind of L3 entry will only contain routed ports in the egress VLAN(s) (instead, a separate L2 entry will bridge in the ingress VLAN).


The igmp-show command offers a high-level view of the dynamic behavior of the feature (in this example, port 15 is the  loopback port):


CLI (network-admin@switch) > igmp-show


group-ip  node-ip  vnet vxlan bd vlan port       source  node-type expires(s)

--------- -------- ---- ----- -- ---- ---------- ------- --------- ----------

<snip>

239.1.1.1 ::                  10   15                  0.0.0.0  host      0    

239.1.1.1 10.1.1.2            10   12 12755068416 0.0.0.0  host      0  


The first line is a Layer 2 entry for group 225.1.1.1 that corresponds to a logical port (1275068416), namely, to a VXLAN tunnel to replicate the multicast traffic to (as it has at least a receiver in the same VNI-mapped VLAN). More than one tunnel may be listed in this position.


The second line is dynamically programmed by the software to send a copy of the multicast traffic for group 225.1.1.1 in VLAN 10 to a special  loopback port (see below)  so that a second (routing) pass after recirculation can be performed. This means that there is a source sending traffic to the group on the ingress VLAN, therefore a L3 lookup can happen for local routing.


The third line (in the show output above) shows IGMP membership on port 19 in egress VLAN 30 (which needs to be routed to).