02-15-2004 07:32 AM - edited 03-02-2019 01:35 PM
I do a show mac in a new Sup2 CatOS 7.6(1) on a 4506 I see some many
ports with Xmit-Multicast equaling about 50% of the traffice. How can I
track down the source. This is only a Layer 2 network, no routers. I am
getting some complaints about Mitel IP Phones cutting in/out that sounds
like lost packets (could be Mitel phone/dsp firmware, but I want my show
mac to be clean before I point to Mitel... Seperately I see show in-lost
and out-lost on almost all the ports, about 5% of traffic.
I plugged into a port and did a sniffer trace. I see multicast traffic with a source of Symbol (we use their wireless phones with Mitel) destination is 01-a0-f8-f0-f0-04. How can I filter multicast from a layer 2 perspective with 4500/6500 switches? There are no routers.
Xmit-Unicast Xmit-Multicast Xmit-Broadcast
-------- -------------------- -------------------- --------------------
1/1 2169314 135905 79417
1/2 0 0 0
2/1 0 0 0
2/2 0 0 0
2/3 764136 513832 890126
2/4 &n bsp; 0
0 0
2/5 765068 513831 890126
2/6 0 0 0
2/7 766945 513832 890126
------------------------------------------------------------------------
02-15-2004 01:25 PM
Hello Jason,
Filtering multicasts is something that you do not want to do. In general, they represent a very low volume of the total bandwidth that is available.
One may get a wrong impression about this when a sniffer is attached to a network port where no other host is active. In that case, you only observe bcast, multicast and unknown destination mac adresses. This may seem a large amount of traffic but it is in fact a very little one.
Regards,
Leo
02-15-2004 01:45 PM
In general I agree, but in this case the multicast traffic across all ports equals about 50% of the unicast traffic, and can't be explained. 50% seems unusual. Why send a broadcast across trunks to hosts that don't need the traffic? Multicast makes switching useless in a layer2 environment. We are back at hubs and bridges..when your hosts are across L3 links multicast is great..
02-16-2004 12:18 AM
Hi,
read following articles:
http://www.cisco.com/warp/public/473/38.html
and
http://www.cisco.com/warp/public/473/22.html
Regards,
Milan
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