Multicast Traffic in a Layer 2 network

[angel-moon]

                  All,

in a network with multiple subnets is there any configuration on Cisco switches needed to allow multicast traffic to traverse all the different subnets? All switches involved are 3750 v2s.

Thanks in advance!  All replies rated.

[Peter Paluch]

Hello,

If I understand you correctly then what you want to achieve is that a multicast traffic originating in one VLAN is flooded to all other VLANs. Am I correct?

If so then you will need to configure multicast routing. Without the multicast routing, a multicast stream will be confined to a single VLAN.

The easiest way to activate multicast routing is to activate a so-called PIM-DM (Protocol-Independent Multicast - Dense Mode) protocol. The configuration would be as follows:

!!!

ip multicast-routing

!

interface Vlan X

  ip pim dense-mode

!

interface Vlan Y

  ip pim dense-mode

!

interface Vlan Z

  ip pim dense-mode

!!!

Use the ip pim dense-mode command on all SVI interfaces where either a multicast stream source is located or where the multicast stream shall be flooded.

Best regards,

Peter

[angel-moon]

Thanks for responding.  They kept insisting there was now Layer 3 involved.  I could not log onto any network devices to prove otherwise.  Turns out there was Layer 3.

Thanks!