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New Member

adsl connection becomes cloggled/slow

cisco 2651XM router with WIC1-ADSL card
IOS: c2600-ipbasek9-mz.124-17.bin

I have a problem with this router in that the adsl connection seems to be getting clogged up or mangled and I lose internet connectivity. It happens about once every day and if I shut down the atm0/0 intterface and then start it again this restores the internet connection. The internet connection isn't completely down but if I ping from the router I get varying success rates from 0% to 80%. Normally the ping is 100% successful. This router has always been rock solid for years however this problem has co-incided with running a linux vpn machine with rtorrent through the router and I thus have a continuous stream of encrypted torrent traffic both ways. Why should this effect the router in this way? and is there a solution to stabilising the connection? should I be using a different IOS?

  • Getting Started with LANs
Super Bronze

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From what you're describing, it may be the torrent flow is filling your pipe which causes issues for other traffic.


If your ADSL has asymetrical bandwidth, and available bandwidth is less than physical interface bandwidth, you might be able to improve the situation by shaping for egress bandwidth and using per flow FQ.  (NB: an interface shaper, alone, might use FQ.)


Managing ingress bandwidth, isn't always feasible.  Policing ingress torrent traffic might help.

New Member

thanks for your response:I

thanks for your response:

I should further mention I do have traffic throttling configured on the torrent program, which controls the speed both in and out at different times of the day (otherwise the traffic would simnply choke up all my bandwidth). So I'm not sure it's a 'choke' problem. Also, once the connection goes down  my vpn tunnel goes down, the torrent traffic stops and nothing will flow properly on the broadband, even non-vpn traffic. I was thinking maybe the type of traffic could be causing a hiccup in the adsl card but I'm not sure, because the main traffic is vpn traffic - which made me think I should use an IOS more suited to it (?). But I don't know if there is an IOS that's friendlier to vpn traffic.

New Member

Hi Tony, the 'IPbase' IOS is

Hi Tony, the 'IPbase' IOS is fine for VPN traffic.

Is this problem still occurring? I'd be curious to check the interface stats to check if packets are being dropped from the buffer, by issuing the  'show interface summary' command.

Ensure 'ip cef' is enabled and turn off 'ip virtual-reassembly' on your active interfaces.

Also, have you monitored your CPU utlilisation on the router with VPN traffic? show processes cpu sorted


New Member

Maybe it's a coincidence.

Maybe it's a coincidence. Maybe the quality of the Internet link got bad without you noticing it.

Can you disable the rtorrent app for a while and see if you still have issues? I'm just guessing.

Hall of Fame Super Gold

What is the bandwidth of your

  1. What is the bandwidth of your DSL link? 
  2. Post the output to the command "sh dsl atm"
  3. How often (during the day) do you see this event happening?