[c-nsp] FWSM blocking multicast traffic between two hosts in sameVlan?

[Arie Vayner (avayner)]

Right. No L3.
The only thing is that because you do not have a complete L3, IGMP is
not really completely there, so you should try and look at disabling
IGMP snooping (link in my last email).

Arie

-----Original Message-----
From: Joann Deng [mailto:liblight at yahoo.com] 
Sent: Saturday, September 01, 2007 21:18 PM
To: Arie Vayner (avayner); cisco-nsp at puck.nether.net
Subject: RE: [c-nsp] FWSM blocking multicast traffic between two hosts
in sameVlan?

Yes, that's correct, both servers are on the same VLAN. So
theoretically, no layer 3 should be involved.


Joann
--- "Arie Vayner (avayner)" <avayner at cisco.com> wrote:

> Joann,
> 
> Just to be sure I get you right, both servers are on the same VLAN 
> behind the FWSM, and the FWSM is not really part of the multicast 
> stream (it does not have to pass through it). Is that right?
> 
> If this is the case, then the FWSM should not affect the multicast 
> stream as both servers are on the same VLAN, and multicast is handled 
> by the L2 mechanism on the 6500.
> 
> When you try to "ping <mcast grp>" - I am not fully sure how would 
> this be sent by the host... I would recommend putting a sniffer on 
> both hosts and making sure the traffic is sent and received correctly.
> 
> Take a look at IGMP snooping:
>
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/122sx/swcg/s
> nooigmp.htm
> 
> It could be that you would have to disable it on these ports (depends 
> on how the applications behave).
> 
> Arie Vayner
> 
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net 
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Joann Deng
> Sent: Saturday, September 01, 2007 00:22 AM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] FWSM blocking multicast traffic between two hosts in 
> sameVlan?
> 
> Hi,
> 
> We have hosts in the same Vlan, which connects to FWSM (routed mode).
> These two hosts run WebLogic, which uses multicast address 
> 237.155.155.2 to communicate.
> But somehow, when run "ping 237.155.155.2" on one host, cannot see 
> response back from the other.
> So, is it possible that FWSM is doing something fancy, like blocking 
> multicast traffic, and we need to add some configs?
> Any input is highly appreciated.
> 
> Thanks,
> 
> Joann
> 
> 
>        
>
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