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New Member

1841 SDSL performance degradation


Any advice would be greatly appreciated!!

I have just added an SDSL wic to slot 1 of an 1841 router, a serial card is already installed to slot 0.

The router was running with c1841-ipbase-mz.124-1c.bin but I have upgraded it to advanced IP services. Initially I had problems with the IOS recognising the SDSL card (c1841-advipservicesk9-mz.123-8.YG4.bin and c1841-advipservicesk9-mz.123-8.T11.bin) but found a thread in the forum suggesting c1841-advipservicesk9-mz.124-5b.bin. After applying this IOS the SDSL card is recognised and I am able to get a connection to the internet (BT SDSL in the UK).

The problem is that the browsing experiece is unpredictable, that is to say it can be perfectly normal but after a few minutes it degrades to unusable, it can then resume without interception. A call has been raised with the ISP but I have tested the connection using a different (non-cisco) router and it works perectly well.

A 1000 byte ping to the internet also yields around 10% packet loss but when tested with a differnet router on the same line there is no loss.

Has anybody else experienced this problem or could they perhaps suggest a more suitable IOS?

Any help greatly appreciated.



New Member

Re: 1841 SDSL performance degradation

Hi James,

I am a novice in cisco stuff, but I have seen this few times with all my DSL connections

My problems were exactly the same as yours and every time I called Cisco, they fixed it by modifying the MTU size.

I am not too sure where the change is, but I think they do it at the interface where your inside hosts are located

I am pretty sure someone here will help you better, meanwhile I will take a look at my routers where I have DSL connections and I will tell you more exactly where is that little trick

hope it helps a bit :)

New Member

Re: 1841 SDSL performance degradation

Thanks for your reply.

I have seen issues before with MTU and DSL lines. Where have you set the MTU? against the interface or the Dialer?


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