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Standard User edweb
(newbie) Fri 12-Jan-07 11:58:06
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Ever decreasing MTU


[link to this post]
 
I have been getting the problem of my MTU value having to be decreased, every now & again my browser won't open any pages so I check the ping value using the 'ping -f -l #### 192.168.1.1' I am now having to set the value to 700 to get a ping response that doesn't fragment the packets. I am running on W2K through a Draytek vigor 2600 router, I have 2 other PC's on the same router so I know the problem must be on the PC & probably a registry entry. Does anybody know what I can do to to remove any rouge entries from my registry which effect the MTU?
Standard User themidgieman
(committed) Fri 12-Jan-07 15:31:13
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Re: Ever decreasing MTU


[re: edweb] [link to this post]
 
In answer to the general PC question I use Registry Mechanic and it's a brilliant program (
Standard User Gypsydog
(fountain of knowledge) Fri 12-Jan-07 15:57:19
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Re: Ever decreasing MTU


[re: edweb] [link to this post]
 
Try using the 'Tweak Test' on this site to diagnose/recommend settings.

http://www.dslreports.com/tools

Then use 'Doctor TCP' - download from the same page - to change your settings to those advised.





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ZyXEL Prestige 660HW-T1





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Standard User edweb
(newbie) Fri 12-Jan-07 16:32:20
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Re: Ever decreasing MTU


[re: Gypsydog] [link to this post]
 
I think I may have found the problem, I was using DRtcp & also DSLreports to try & find the problem. I found that to reset to the default values just set everything in DRtcp to blank then reboot. I did this & I can now ping at 1472. It seems that DRtcp was causing the problem probably there were other settings that were conflicting. What I need now is a way of checking what MTU setting I am actually using. I do have a copy of System Mechanic I will have a look to see if that can help.

Ed
Standard User E7er
(fountain of knowledge) Fri 12-Jan-07 19:28:47
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Re: Ever decreasing MTU


[re: edweb] [link to this post]
 
I prefer to find the MTU this way,
Finding the largest MTU by EXPERIMENT version 2

First reset windows with Dr TCP to MTU 1500.
Then reset modem/router to MTU 1500 save it, reboot PC and modem/router.

Next from windows, go to Start/Run and type in, cmd (click OK)
At the MSDOS-PROMPT type,

ping -f -l 1472 www.bbc.co.uk

Then reduce 1472 by 10 until you no longer get the "packet needs to be fragmented" error message or

http://www.ezeedsl.co.uk
ezeeDSL 2Mbps unlimited-uncapped-unmetered with static IP address
3Com 3CRWDR100A-72-UK ADSL2/2+ modem/router uses Texas Instruments AR7 Chipset
Downstream actual speed 1925Kbps
Upstream actual speed 246Kbps
Standard User edweb
(newbie) Fri 12-Jan-07 20:26:49
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Re: Ever decreasing MTU


[re: E7er] [link to this post]
 
This is what I had done, the problem was the MTU would every so often decrease?? Sometimes I could check it & increase it back, all the time I was using DRtcp to change it. Lately though I was unable to open any webpages without checking the MTU using 'ping -f -l .....' then set it using DRtcp. Now I've wiped all the settings from DRtcp - saved then rebooted I can now 'ping -f -l .....' at 1472. I don't know what was happening but DRtcp seemed to be causing the problem, I was having to set the MTU to 700 before I could get it not to fragment. I would like to find out though how I can check what my MTU is now set to, I'm sure I used to have a dos comand for checking this & also changing it but I can't remember what it was.

Ed
Standard User themidgieman
(experienced) Thu 08-Feb-07 12:31:32
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Re: Ever decreasing MTU


[re: themidgieman] [link to this post]
 
Sorry to drag back this old thread. Just found out that pctools via element 5 may have set up an annual cca for this product, whereas I made a one-off purchase. In the light of that I withdraw my recommendation for this product, apologies to anyone who may have been inconvenienced by my recommedation

Edited by themidgieman (Thu 08-Feb-07 12:55:37)

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