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   Distributed Multicast Forwarding scope - fabric or local

disable disable DM Forwarding

enable  enable 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     vlan vrid hw-group-id send-vlan ports  flags

------- --------- ---- ---- -----------  ---------  ----- ------  501  0    0x200098a     0         none  Active  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 (*,, 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 VXLAN loopback port):

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

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

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

<snip> ::                10   1275068416 host      0 ::                10   15 host      0          30   19 host      279  

The first line is a Layer 2 entry for group 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 in VLAN 10 to the loopback port 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).