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Posts: 17
Joined: Tue Oct 18, 2005 4:39 pm
Location: Dublin, Ireland

Block massive broadcast and/or Large numbers of small packet

Fri Sep 25, 2009 12:38 pm

Senario is as follow:

Flat network, no routing apart from edge, every now and again we are experiencing massive latency accross the network. After a lot of trudging we have nailed this down to being either massive amounts of broadcast traffic flooding the network and/or massive amounts of small packets (+/- 40 bytes).

Does anyone have or is anyone able to write whatever scripts required to block or restrict this traffic, we have tried a number of rules and they seem to either be blocking too much or not blocking at all.

Or alternatively can someone point out where we are going wrong, I know the flat network is an issue but we are nearly finished our submission for public IP's and have no choise but to wait until it is complete as we don't want to change everything twice.

These are two samples of rules we have tried,

4 X ;;; drop small packets
chain=forward action=drop protocol=tcp src-address-list=small-packets

5 X ;;; smal packets list
chain=forward action=add-src-to-address-list protocol=tcp
address-list=small-packets address-list-timeout=1h limit=200,5

Please help!!!!

Many thanks in advance
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Posts: 6283
Joined: Tue Feb 14, 2006 9:46 am
Location: Riga, Latvia

Re: Block massive broadcast and/or Large numbers of small packet

Mon Sep 28, 2009 11:01 am

you are using bridges? do you have loops in your network? What you mean by flat network?

for bridges use rstp for loop detection, and you should be able to avoid broadcast "storms", in case of STP mode - these problems are resolved very slowly (10 - 30 minutes) with none - these problems are not solved at all.

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