Multicast

In Ethernet networks, sending multicast feed to multiple receivers in multiple VLANs causes the replication of the same multicast traffic for every VLAN resulting over-utilization of the bandwidth. Multicast VLAN Registration (MVR) eliminates this by sending multicast traffic only on the dedicated multicast/source VLAN. Then this multicast/source VLAN feeds all the multicast receivers residing in multiple VLANs.

Here R1 is the multicast source and R2 is the receiver. All devices (including SW1) are running PIM dense mode between them and are using EIGRP for the basic connectivity. MVR has been configured on SW1 with VLAN17 being the multicast/source VLAN for the group 235.1.1.1 which is feeding the receivers on VLAN27 for that multicast group. Let's check the relevant configuration on those devices:

"ip multicast multipath" allows to load split (not load balance) multicast traffic from different sources for the same multicast group across multiple equal-cost paths. Let's go to the example to make it clear:

So what is the use of "filter-autorp" option in the "ip multicast boundary" command? Let's explore it with an example:

Here R3 is the multicast source and R2 is the client. R1 is serving as RP the for multicast groups 226.0.0.0/8, 228.0.0.0/8, and 232.0.0.0/5. R1 ia also the mapping agent. Let's check the relevant configuration on those routers:

In Cisco IOS, "ip multicast rate-limit ..." command allows us to rate-limit IP multicast traffic to a desired rate. Once the configured limit has been reached, further data that would exceed this limit is discarded.

Let's do a quick example on this. Below is an output from a router without any multicast rate-limit configuration:

Rack1R4#sh ip mr | sec 235\.0\.0\.1|236\.0\.0\.1
(*, 236.0.0.1), 00:18:28/00:02:58, RP 150.1.2.2, flags: SCL
  Incoming interface: Ethernet0/0, RPF nbr 180.1.47.7
  Outgoing interface list:
    Loopback0, Forward/Sparse-Dense, 00:18:28/00:02:35
(*, 235.0.0.1), 00:18:28/stopped, RP 150.1.2.2, flags: SJCL
  Incoming interface: Ethernet0/0, RPF nbr 180.1.47.7
  Outgoing interface list:
    Loopback0, Forward/Sparse-Dense, 00:18:28/00:02:35
(180.1.17.1, 235.0.0.1), 00:18:26/00:02:58, flags: LJT
  Incoming interface: Ethernet0/0, RPF nbr 180.1.47.7
  Outgoing interface list:
    Loopback0, Forward/Sparse-Dense, 00:18:26/00:02:35
(180.1.37.3, 235.0.0.1), 00:01:45/00:02:58, flags: LJT
  Incoming interface: Ethernet0/0, RPF nbr 180.1.47.7
  Outgoing interface list:
    Loopback0, Forward/Sparse-Dense, 00:01:45/00:02:35

From the above output, we can see two (S,G) flows for the group 235.0.0.1 and a (*,G) flow for the group 236.0.0.1.

Lets go to the rate-limiting part. Multicast rate-limiting can be done in two ways: