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Old 04-13-2009, 04:28 PM   #1
Registered: Sep 2008
Location: Dominican Republic
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Help blocking torrents


Our network has experienced a slow down as late, I noticed people are downloading stuff with bittorrent and other torrent clients. I would like to know how to block these or throtle them. I don't know what ports are used by these clients. I've searched on google but, no luck on finding which ports are used by the torrent clients.

Please help. thanks.
Old 04-13-2009, 05:21 PM   #2
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Simple answer: Block port 6881. That might do something. Not-so-simple answer: The traffic will probably find a way around you blocking ports. Your best bet would be to use Qos software to throttle the traffic.
Old 04-13-2009, 05:24 PM   #3
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Additionally, depending on your scenario it might be time to look at revisiting network access policies. (e.g. Force them to pass through a gateway/http proxy?)
Old 04-13-2009, 05:25 PM   #4
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Take a look at
Old 04-13-2009, 08:25 PM   #5
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most people are no longer using port 6881
just take a look at the leaches to see, that the ports go from 6881 ( a few) to 65,000
Old 04-13-2009, 08:45 PM   #6
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I know is going to be hard to prevent users from using these torrent clients, I guess the easiest way is just to throttle that traffic. Only give certain amount of bandwidth to those ports. Now, today I used ethereal to analyze some traffic and I noticed BitCommet uses tcp protocol instead of udp. That caught me by surprise. I thought it was supposed to use udp protocols.

I would like to use tc / iptables to assign only 56kbps to those traffic with a low priority. Maybe this way, the network speed would get better.

What would happen if I did this:

iptables -t mangle -A FORWARD -o $ext -p udp --dport 1025:65535 -j MARK --set-mark 1

iptables -t mangle -A FORWARD -o $ext -p tcp --dport 1025:65535 -j MARK --set-mark 1

and use tc to throttle bandwidth to 50kbit to all the packet with mark 1?

What would happen to voip, bittorrents, etc... Would my idea work here?

Last edited by landysaccount; 04-13-2009 at 09:16 PM.


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