Any Cisco CCNA engineer able to help?

[tfboy]

I'm working on a network system which has 2 Cisco Catalyst 6500 switches.

The two switches have very simple configurations: all interfaces are attached to VLANs, each VLAN having his own gateway so traffic can be routed between vlans.

The two switches are linked together via a port-channel trunk, comprised of 6 gigabit ethernet ports bundled together.

I have a really stupid issue making me go bald right now:

there is a "Server A" attached to VLAN A on Cisco_1 which runs a jini lookup service. This broadcasts via udp multicast on 224.0.1.85.

Workstations A, B, C and D physically connected to Cisco_1 receive the multicast and responds with directed TCP packet.

However, workstations E, F, G and H physically connected to Cisco_2 do not pop into life.

I've setup a few monitoring sessions on some spare ports to see what happens at the physical interface level. Monitoring port A wich connects to Workstation A for example shows the receipt of the multicast packets.

Monitoring port F which connects to Workstation F on the second cisco receives no multicast packets.

So for some reason, the multicast is not getting across the switch. How come? All other traffic seems to hit the port and because both sets of ports are attached to the same VLAN, there shouldn't even be any routing required. So I'm and also

Any ideas.Pretty pretty please? I've already slapped my wrist for not buying Smartnet

Config files available via PM if anyone can actually help

TIA :thumbup:

[GDVS]

I'm not a CCNA and not even remotely qualified to set up multicast (done it once just for kicks, never again) but I believe you need to enable the IGMP snooping querier on Cisco_2. Try "ip igmp snooping querier" to enable what amounts to an IGMP proxy and hopefully that will work.

[tfboy]

Thanks I'll give it a try

[badass]

I cant quite tell from your post if all workstations are on the same VLAN?
If they are then I haven't a clue. If they are on different VLANs then the problem could be incorrect setting up of multicast boundaries on the router* that connects the 2 VLANs



When I say router I really mean the switch acting as a router as they are layer 3 switches and I presume you are using them as such

[Paul Adams]

I cant quite tell from your post if all workstations are on the same VLAN?

"All other traffic seems to hit the port and because both sets of ports are attached to the same VLAN, there shouldn't even be any routing required."

GDVS's suggestion sounds the most likely cause - at least 1 switch needs the IGMP snooping querier enabled.

[tfboy]

Hi Guys

Well well well, eventually found what was causing it You were right. By default, the Cisco actually blocks multicasts by IGMP snooping. I've disabled it by "no ip igmp snooping" on both switches, and the multicasts are now effectively broadcast between the two switches and everything's working.

You can have an "mrouter" enabled to more precisely manage the traffic and probably limit which ports on which switches the multicast is actually transmitted to.

All the gory details here: http://www.cisco.com/en/US/products/...8059a9df.shtml

Thanks for the input

[tfboy]

If anyone's interested, I've changed it now to use the PIM sparse dense mode / mrouter as it does effectively keep the IGMP querying going on. I was concerned that some devices on the network have very little networking power so having turned off IGMP snooping, they were effectively having to manage the multicast which was being broadcast to all devices on the VLAN.

Still working so happy bunny. Guess it almost makes a supervisor engine 720 represent good value for money