1801 router and really slow internet access

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Aug 5th, 2010
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I am a CISCO novice so I really have no idea where to start with this. We have a Cisco 1801 router connected to an 8MB ADSL line. Up to about a month ago it was working fine. Internet access and download speeds were pretty good. However it has started playing up and while we can still generally access web pages (although sometimes it takes a couple of refreshes to get them rendered correctly), if we try to download any reasonable size of a file you can forget it. They will download so far then just stop (and this includes thigs like out antivirus definitions and anti-spam rules)


I had our ADSL line tested and it is fine. I also took our local network out of the equation by disconnecting our switch and connecting just one PC into the router switch ports but that made no difference either. Finally I reconnected our old Draytek router to the DSL line and everything worked perfectly hence I'm pretty sure something is up with the 1801.


I have attached the running config but any help on how to diagnose or resolve this would be greatly appreciated!

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Nagaraja Thanthry Thu, 08/05/2010 - 17:50
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Hello,


Can you post the output of "show interface" command here? Also, you could try removing the inspects and see if the performance improves.


interface Dialer0

no ip inspect SDM_LOW out


Hope this helps.


Regards,


NT

melladoosra Thu, 08/05/2010 - 19:03
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Maybe your router is bogged down with NAT translations.


Issue the "show ip nat translations" cmd and see what you get. Chances are there will be heaps there.


Then try clearing them with the clear ip nat translations * cmd

miroofi75 Fri, 08/06/2010 - 06:08
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Dear Richard,


add following may be it will helps:


ip inspect max-incomplete high 900
ip inspect max-incomplete low 700
ip inspect tcp idle-time 1800
ip inspect tcp synwait-time 60
ip inspect tcp max-incomplete host 128 block-time 0


adjust high, low, idle-time, synwait-time and host as per your requirement.


regards,


Imran

paolo bevilacqua Fri, 08/06/2010 - 06:25
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Actually the best approach is to remove ip inspect altogether, as correctly suggested above.

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