DSL and 1841

Unanswered Question
Jul 10th, 2007

I am having an issue with my DSL connection and my 1841. The DSL line is a 3MB connection, if I connect directly through my laptop I can run a speed test and get 3MB. Once I put the connection to the 1841 my speed runs any where from 400K to 545k. Can someone assist me in trouble shooting the issue.

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Richard Burts Tue, 07/10/2007 - 10:16

Chris

The first thing that I would look for is potential mismatch of duplex. Is the 1841 set for speed auto and duplex auto or do you set speed or duplex?

It might be helpful if you could post the config of the 1841.

HTH

Rick

chris.iseral Thu, 07/12/2007 - 07:24

Hi,

when i remove the ip inspect command from the config, for some reason I lose connection to the outside. I used the SDM to set the connection up, I believe it might be part of the issue as well. I am looking for a sampe config for PPPOE. I have another question, the service provider states to use MS-CHAP but the only option is CHAP would this be causing the issue. At this point I have taken the router down completely and redone the config with out the firewall and IPS, VPN or anything and I still get the same results. I have even switched to a different router and still had the same issue.

Richard Burts Thu, 07/12/2007 - 07:44

Chris

MS-CHAP (or CHAP) is used for authentication when the connection is established. I believe that if this were an issue that the connection would not be coming up - it would not be slow, it would be broken.

I wonder if the issue might be MTU related. When you run PPPOE it adds some additional to the header. If the laptop is directly connected it probably reduces the segment size to accommodate. But if the laptop is connected to a router it is probably sending full size Ethernet frames. Adding the extra info for PPPOE might cause it to be larger and require fragmentation. You might experiment with configuring ip tcp adjust-mss on the LAN interface specifying a smaller segment size and see if performance improves.

HTH

Rick

chris.iseral Thu, 07/12/2007 - 12:15

Ok I have change the adjust-mms, i got it all the way down to 1050 and can really see not difference, I did get 399kbps which is the fastest yet but it wasnt with the mms set at 1050. I notice during the test the bandwidth will run up to 700k then come back down slowly, would the be a mtu setting with thte dialer that might need to be changed. Attached is a sample config the ISP sent to me, let me know if i should use this to configure.

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Richard Burts Thu, 07/12/2007 - 12:40

Chris

I am somewhat confused. You are working on an 1841. The config that you attached is for a PIX. What is the relationship of the PIX and the 1841?

HTH

Rick

chris.iseral Fri, 07/13/2007 - 04:56

It has nothing to do with it, it is just what the ISP sent to me. I thought maybe it would be helpful. I have adjusted the mtu all over the place and it does not seem to make much of a diffrence.

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