Powerconnect 6024F and multicasting

Question

Ok here is the issue i am having. Currently i have 2 6024F that act as a core switch with a 7gig fiber link between them. On one side I have my novell server, my fiber link to the other building, and all my XP workstations. On the other side i have my MAC's, X-Server, and my ISP link. I use Ghost to image all my XP workstation and i know these switches support multicasting. However, the switches at my other buildings do not support multicasting. Currently if i multicast, it is broadcasted through my fiber line to the other buildings and those switches crash. Is there i way to block the multicast from being broadcasted to the port that my fiber uplink is connected to.

GregG1 · Answer

To allow dynamic multicast registration, you would need to enable IGMP Querying on one of the 6024s and enable IGMP Snooping and Bridge Multicast Filtering on both switches.

To enable IGMP Querying for VLAN 1, you would use the following commands:

console# config
console(config)# interface vlan 1
console(config-if)# ip igmp

To enable IGMP Snooping and Bridge Multicast Filtering on VLAN 1, you would use the following commands:

console# config
console(config)# ip igmp snooping

console(config)# bridge multicast filtering
console(config)# interface vlan 1
console(config-if)# ip igmp snooping

With IGMP querying and snooping enabled, multicast streams should only be sent to ports containing members of the multicast group.

For more information regarding IGMP and IGMP Snooping, see the online CLI Guide at the following links:

IGMP - < ADMIN NOTE: Broken link has been removed from this post by Dell>

IGMP Snooping -

schwartzmeier · Answer

I had the snooping enabled but did not know that i needed IGMP Querying enable on one of the switches. I'll be trying that shortly. Thanks Again!

schwartzmeier · Answer

This is my current config file.

conf

hostname A220-6024F-01

int vlan 1

ip address 10.0.10.1 255.255.0.0

ip igmp

ip igmp snoop

exit

ip igmp snoop

bridge multi filter

username admin password xxxxxxxx level 15

ip http auth local

aaa auth login default local

enable password xxxxxxxx

ip route 0.0.0.0 0.0.0.0 10.0.0.6

interface range ethernet g(1-7)

channel-group 1 mode on

exit

The 2nd switch is almost the same just minus the IP IGMP on vlan 1.

However, it is still broadcasting to my fiber link to the other buildings. I know i am missing something. Any idea what im missing?

-Jim

Message Edited by schwartzmeier on 12-08-2004 11:19 AM

Message Edited by schwartzmeier on 12-08-2004 11:23 AM

aksearle · Answer

Jim

I have an on going problem with a couple of Powerconnect 5212's that have IGMP snooping and IGMP Querier running on them. If they receive multicast data addressed to a group for which they have no hosts connected that have actually joined tha group, they revert bact to broadcasting it on all ports. I would expect this with a stardard L2 switch but not one with IGMP snooping and IGMP Querier running.

So far Dell have been unable to provide a reason why this is happening except to say I need a L3 router in my network......but again, not why I need one!!

regards
Andy

schwartzmeier · Answer

Before i purchased these switches we had a demo switch. This was before my time so i am not aware of the config of it. However, they are 100% sure that they were able to multicast and not bring down my other switches. In fact, they believe they were able to multicast through the other switches as long as the host machine was on the Dell switch. I wish i knew what model and the config of the switch they demo'd. Although i find this hard to believe that they could multicast through my Catalist 4006 with a supervisor II board in it. But they say they could. I wish i had an answer to this problem because the main reason i went with Dell on these switches was because i was able to multicast with them. I really do not want to unicast in my new building. I hope i didn't waste money on these switches.   -Jim

GregM_1 · Answer

Aksearle,

The 5212s are working as they should. The IGMP querier feature is only used if you have no router. This in turn helps IGMP snooping do its job. If an unknown multicast group enters the switch, and their is no mapping for it, or no one is subscribed, it floods. This is normal layer 2 behavior.

By having the IGMP querier feature enabled, you can trigger a response for join/leave requests, which in turn the IGMP snooping feature can 'hear' and map to the appropriate port.

The only way to keep unknown multicast groups from flooding is to stop them at a layer 3 interface, which the 5212 does not support. I believe your are confusing the ability of the 5212 to use a layer 3 feature such as IGMP querier as the ability to be a total layer 3 switch.

GregM_1 · Answer

Schwartzmeir,

Your issue sounds similar to the one above. You are having multicast traffic cross your fiber. This would be expected because it seems you have both 6024s in the same VLAN 1. There is no layer-3 interface defined. Therefore, unknown multicast groups will still flood. In addition, if any node across the fiber 'hears' the IGMP querier it may decide to 'join' and then the multicast stream will be propagated across the link.

What you can do is put the uplink into a different subnet. The make sure you enable DVMRP. This will stop all multicast traffic at the layer-3 interface and will only route a multicast stream if it 'hears' a 'join' request from the other subnet.

schwartzmeier · Answer

If i were to put the uplink in a different subnet wouldn't that take away from my flat network design. Currently, the network sees' itself as if it was in one location.   Thanks for all the help so far!   -Jim

GregG1 · Answer

Schwartzmeier,   I apologize for the delay, but I needed to perform some testing on this issue to determine the cause of the problem. I setup a similar scenario (using a 6024 and two 5324 switches) and used VideoLAN to test the multicast stream. I was able to duplicate the same problem you are seeing.   After extensive email correspondence with the OEM vendor, we have found the source of the problem. We found that the 6024 must be configured with the global command 'ip multicast-routing' in order for it to recognize itself as the IGMP Querier. Without this command, the switch does not register a Querier router (itself) and the multicast traffic is flooded to all ports on the VLAN.   This information was previously not documented and the 'ip multicast-routing' command was only referenced in relation to DVMRP. In your scenario, you should be able to configure one of the 6024s to provide the querier and multicast-routing functions as well as igmp snooping and bridge multicast filtering. The second 6024 should only need to be configured for igmp snooping and bridge multicast filtering.

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Powerconnect 6024F and multicasting

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