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TOPIC: multicast storm in wireless network

multicast storm in wireless network 12 years 2 months ago #5273

  • Heretic
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I'm in the process of adding wireless capablities to our lan. I've installed the first 3com access point (11g) and it works great.

I'm experiencing the following problem:

whenever I install the second Access Point, my network slows down considerably. After some investigating, I noticed that multicasts went from an average of 50-80 to 2900+ as soon as the second AP was powered on. I see a tremendous amount of retransmissions, acks, etc. I've swapped out the AP's but I still get this problem. I need to install 8 AP's.

Has anyone come across this problem? 3Com was no help.
I have a simple nt4 network with about 200 users.

nt4 domain
1 pdc, 2 bdc
win2000 server for dhcp

Thanks
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Re: multicast storm in wireless network 12 years 2 months ago #5280

  • sahirh
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If possible could you post a small capture file with samples of the traffic so that we can analyse it. Are you sure its multicast traffic ? 802.11 does generate a lot of administrative overhead in the form of beacons etc.
Sahir Hidayatullah.
Firewall.cx Staff - Associate Editor & Security Advisor
tftfotw.blogspot.com
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Re: multicast storm in wireless network 12 years 2 months ago #5301

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Sahir,

thanks for replying. How do I go about attaching a file? Can you use a sniffer 4.5 format?

On the sniffer dashboard, the multicasts/s shoots up from 50-80 to currently 3047, all other values being about the same. This happens as soon as I plug in the second access poin, and disappears when I unplug it.

packets/s = 3044
utilization = 2
errors/s = 0
drops/s = 0
bytes/s = 228021
broadcasts = 2
multicasts/s = 3036

Thanks

Emin
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Re: multicast storm in wireless network 12 years 2 months ago #5316

  • sahirh
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Hmm if you have a little bit of space to upload the capture files to it would be a good idea.. maybe a geocities account or something.

I guess the sniffer file format should do.. see if it can save as a libpcap packet capture file since thats more universally supported. No need to give a whole lot of traffic, just a small sample is fine.
Sahir Hidayatullah.
Firewall.cx Staff - Associate Editor & Security Advisor
tftfotw.blogspot.com
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