If the problem shows up as a ping storm, you could try something like the 
following, but to be really effective it needs to be running near the edge 
of your network (e.g. the client AP):

iptables -N lmticmp
iptables -F lmticmp
iptables -A lmticmp -j ACCEPT -s ! 192.168.0.0/16
iptables -A lmticmp -j ACCEPT -s 192.168.0.0/16 -m limit --limit 30/s
iptables -A lmticmp -j LOG -m limit --limit 5/min --limit-burst 
5 --log-level 0 --log-prefix "PACKETSTORM"
iptables -A lmticmp -j DROP

There's also a good posting on this subject here:

http://www.usenet-forums.com/linux-networking/59497-what-limitation-iptabless-limit-option.html

Tom Sharples
Qorvus Systems, Inc.


----- Original Message ----- 
From: "Dennis Burgess" <[email protected]>
To: "WISPA General List" <[email protected]>
Sent: Wednesday, February 18, 2009 9:58 AM
Subject: Re: [WISPA] Suggestions on preventing network flooding


> As I say in my Traffic Management and Firewalling Mikrotik Courses,  "If
> you can't identify the traffic, you can't control it, block it, limit
> it, or otherwise do ANYTHING with it! "
>
> Traffic Identification is first! :)
>
> * -----------------------------------------------------------
> Dennis Burgess, CCNA, A+, Mikrotik Certified Trainer
> WISPA Board Member - wispa.org <http://www.wispa.org/>
> Link Technologies, Inc -- Mikrotik & WISP Support Services
> WISPA Vendor Member*
> *Office*: 314-735-0270 *Website*: http://www.linktechs.net
> <http://www.linktechs.net/>
> */LIVE On-Line Mikrotik Training/*
> <http://www.linktechs.net/onlinetraining.asp>
>
> The information transmitted (including attachments) is covered by the 
> Electronic Communications Privacy Act, 18 U.S.C. 2510-2521, is intended 
> only for the person(s) or entity/entities to which
> it is addressed and may contain confidential and/or privileged material. 
> Any review, retransmission, dissemination or other use of, or taking of 
> any action in reliance upon, this information by persons or entities other 
> than the intended recipient(s) is prohibited, If you
> received this in error, please contact the sender and delete the material 
> from any computer.
>
>
>
>
>
> Patrick Shoemaker wrote:
>> You really need to find out exactly WHAT the problematic traffic is
>> before you worry about how to best block it. Hook up a machine with
>> Wireshark to a tap or a mirrored switch port that is seeing the
>> offending traffic. If you can't immediately identify the problem traffic
>> by looking at the packets live from the wire, you can have Wireshark
>> sort the flows by all kinds of different factors.
>>
>> Patrick Shoemaker
>> Vector Data Systems LLC
>> [email protected]
>> office: (301) 358-1690 x36
>> http://www.vectordatasystems.com
>>
>>
>> Patrick Nix Jr. wrote:
>>
>>> Right, I'm routing already to my customers. I just can't seem to
>>> identify where the flood of traffic is coming from.  My guess is that
>>> someone is using some sort of p2p and opening gazillions of connections
>>> for either upload or download traffic or someone has a virus that is
>>> flooding the network with a bunch of small packets.  I've tried to setup
>>> some iptables rules in our imagestream to prevent both of these but I am
>>> a newbie with iptables and I either end up killing all internet traffic
>>> to everyone or it has no effect at all.  Does anyone care to share some
>>> suggestions for iptables rules using Powercode with an imagestream
>>> router.
>>>
>>> Thanks a million.
>>>
>>> __________________________________________
>>>
>>> Patrick Nix, Jr.,
>>> csweb.net
>>> (918) 235-0414
>>> http://www.csweb.net
>>> E-Mail: [email protected]
>>>
>>> ====================================================================
>>> ATTENTION: This e-mail may contain information that is confidential in
>>> nature. If you are not the intended recipient, please delete this e-mail
>>> and notify the sender immediately. Thank you.
>>> ====================================================================
>>>
>>>
>>> -----Original Message-----
>>> From: [email protected] [mailto:[email protected]] On
>>> Behalf Of Dennis Burgess
>>> Sent: Wednesday, February 18, 2009 10:33 AM
>>> To: WISPA General List
>>> Subject: Re: [WISPA] Suggestions on preventing network flooding
>>>
>>> Routing man.
>>>
>>> * -----------------------------------------------------------
>>> Dennis Burgess, CCNA, A+, Mikrotik Certified Trainer
>>> WISPA Board Member - wispa.org <http://www.wispa.org/>
>>> Link Technologies, Inc -- Mikrotik & WISP Support Services
>>> WISPA Vendor Member*
>>> *Office*: 314-735-0270 *Website*: http://www.linktechs.net
>>> <http://www.linktechs.net/>
>>> */LIVE On-Line Mikrotik Training/*
>>> <http://www.linktechs.net/onlinetraining.asp>
>>>
>>> The information transmitted (including attachments) is covered by the
>>> Electronic Communications Privacy Act, 18 U.S.C. 2510-2521, is intended
>>> only for the person(s) or entity/entities to which
>>> it is addressed and may contain confidential and/or privileged material.
>>> Any review, retransmission, dissemination or other use of, or taking of
>>> any action in reliance upon, this information by persons or entities
>>> other than the intended recipient(s) is prohibited, If you
>>> received this in error, please contact the sender and delete the
>>> material from any computer.
>>>
>>>
>>>
>>>
>>>
>>> Patrick Nix Jr. wrote:
>>>
>>>> Everyday we seem to have this problem, we can watch our pings and for
>>>> the morning our avg ping time will be about 27ms to our customers.
>>>>
>>> And
>>>
>>>> then it will just start climbing up to 1000ms and stay there most of
>>>>
>>> the
>>>
>>>> time for hours.  I can't seem to identify where it is coming from
>>>> although it must be coming from our customers, because I can set here
>>>>
>>> at
>>>
>>>> the head end and still ping google at 60ms consistently while this is
>>>> going on.  When it happens the network slows down to the point of
>>>>
>>> being
>>>
>>>> unusable.  Any suggestions. Below is an example of yesterday.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Thanks
>>>>
>>>>
>>>>
>>>> __________________________________________
>>>>
>>>>
>>>>
>>>> Patrick Nix, Jr.,
>>>>
>>>> csweb.net
>>>>
>>>> (918) 235-0414
>>>>
>>>> http://www.csweb.net <http://www.csweb.net/>
>>>>
>>>> E-Mail: [email protected]
>>>>
>>>>
>>>>
>>>> ====================================================================
>>>>
>>>> ATTENTION: This e-mail may contain information that is confidential in
>>>> nature. If you are not the intended recipient, please delete this
>>>>
>>> e-mail
>>>
>>>> and notify the sender immediately. Thank you.
>>>>
>>>> ====================================================================
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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