I have a question about Can't access some websites while using a shared PPPoE connection:

I am connecting 2 windows 2000 PCs via 100Mbps LAN. The highest MTU value that returned a positive ping was 1472, so I adjusted the MTU registry of the client PC. I rebooted but still could not access some websites - same problem. I check the MTU value, but now 1472 returned an error message indicating it must be fragmented. I repeated the pinging test to find a new MTU value that worked - this time 1444 was successful. After modifying the MTU registry entry and rebooting, the same problem occurred. So again I retested and found a lower MTU value that worked. But the problem is still continuing. Why is the successful MTU value changing? I have not rebooted or modified my gateway PC during this process.

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I had the same problem on a win2k network. I found an MTU value, 1416, that finally worked. Strange thing is a value higher OR lower than 1416 would not ping to certain websites. I'm using 384K frame relay, but perhaps 1416 will work for you too. Also, make sure that you are changing the MTU value for all of the applicable interfaces for each PC as well as checking to see that the new hex value is held in the registry after you enter your new values.


On Monday, April 15, 2002 at 3:58 pm, Kydas wrote:
>I have a question about Can't
>access some websites while using a shared PPPoE connection:

>I am connecting 2 windows 2000 PCs via 100Mbps LAN. The highest MTU value that returned
>a positive ping was 1472, so I adjusted the MTU registry of the client PC. I rebooted
>but still could not access some websites - same problem. I check the MTU value, but
>now 1472 returned an error message indicating it must be fragmented. I repeated the
>pinging test to find a new MTU value that worked - this time 1444 was successful.
>After modifying the MTU registry entry and rebooting, the same problem occurred.
>So again I retested and found a lower MTU value that worked. But the problem is still
>continuing. Why is the successful MTU value changing? I have not rebooted or modified
>my gateway PC during this process.

[Reply or follow-up to this message]

On Monday, April 15, 2002 at 8:43 pm, Sean wrote:
>I had the same problem on a win2k network.  I found an MTU value, 1416, that finally 
>worked.  Strange thing is a value higher OR lower than 1416 would not ping to certain 
>websites.  I'm using 384K frame relay, but perhaps 1416 will work for you too.  
Also, 
>make sure that you are changing the MTU value for all of the applicable interfaces 
>for each PC as well as checking to see that the new hex value is held in the registry 
>after you enter your new values.
>

I have the same problem as the one you answered.

Are you saying that I need to set a lower MTU value not only for my client machine 
but also for the client-host connection and the host-interenet connections on my 
host machine?

Thanks in advance,
Uri Goldstein.

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It was necessary for me to set the MTU value on each network interface card (servers, clients, etc.)


On Sunday, June 16, 2002 at 2:36 pm, Uri Goldstein wrote:

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There are 28 bytes in the header, which you should add to the ping data to get the MTU. Thus 1472-28=1444.


On Monday, April 15, 2002 at 3:58 pm, Kydas wrote:
>I have a question about Can't
>access some websites while using a shared PPPoE connection:

>I am connecting 2 windows 2000 PCs via 100Mbps LAN. The highest MTU value that returned
>a positive ping was 1472, so I adjusted the MTU registry of the client PC. I rebooted
>but still could not access some websites - same problem. I check the MTU value, but
>now 1472 returned an error message indicating it must be fragmented. I repeated the
>pinging test to find a new MTU value that worked - this time 1444 was successful.
>After modifying the MTU registry entry and rebooting, the same problem occurred.
>So again I retested and found a lower MTU value that worked. But the problem is still
>continuing. Why is the successful MTU value changing? I have not rebooted or modified
>my gateway PC during this process.

[Reply or follow-up to this message]

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