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Question about Multicast Routing on Cisco 6509

Quick question.

We are doing PIM-Sparse-Dense on a VLAN interface, which has no defined IP.  Since the switch is a L3, I am presuming that not assigning an IP to the VLAN INT means that it's acting as a L2 route in all intent and purpose?... However, after running the following commands, we were able to get Multicast to work:

Interface Vlan 540

ip address

ip pim sparse-dense-mode

no ip igmp snooping


----> My question.  After we enabled this and saw the MC packets come through, we issued a NO IP ADDRESS command (for various internal approval reasons) and the Multicast traffic continued to function.  I stopped and started the Multicast stream and it worked for about 20 minutes after the IP address was removed from that VLAN Interface.  Eventually the stream ceased to function after that timeframe.

My question - can we establish/define a static Multicast Route (or ARP Route) to handle this 'routing' without actually assigning an IP to the Interface itself.  I understand conceptually how this needs to look (I'm just not sure where it needs defining), but if there is a way to handle the request in a static table entry, that would be preferred.

ARP may not be the right reference.. but I guess I just need to know if this can be done, how is the best & most effective way (besides assigning an IP to that Interface directly)?

Thank you in advance!

Adrian Lazar

Hi Brian,

Are you looking to transmit the multicast stream locally, meaning in the same vlan ? If this is the case you need to either enable igmp querier ("ip igmp snooping querier") or PIM on that interface both requiring that you have an IP address configured. On the other hand, if you already have an L3 device in that subnet that can become the IGMP querrier then you don't need an IP on the 6500 vlan interface.

The querier's purpose is to poll the multicast hosts periodically. When the multicast hosts respond with Membership Reports igmp snooping registers them and sends the multicast traffic to the ports.

If your goal is to transport multicast traffic between vlans you must use PIM and have an ip address on the vlan interface.