[afnog] gre on PPPoE

[Chris Liljenstolpe]

I would concur that this sounds like an MTU problem.   See what size  
packets the application is sending (and have someone at the other end  
see what size the return packets are).  Then ping with those sizes,  
and see if the ping fails.

Setting the MTU lower on the VPN routers MAY help (depending on DNF  
bits being set (or not), etc).

	Chris

On 12 Jun 2007, at 18.35 , Siwangu Mgata wrote:

> Thanks Stephane,
>
> The application runs perfectly on a plain IP link.
>
> When the VPN is up, other TCP apps runs well except the Data Store
> (Banking ) application.
>
> The same application runs perfectly when i create a VPN over VSAT and
> wireless networks.
>
> Rgds,
>
> Siwangu
>
>
> ----- Original Message -----
> From: "Stephane Bortzmeyer" <bortzmeyer at nic.fr>
> To: "Siwangu Mgata" <svmgata at sihebs.co.tz>
> Cc: <afnog at afnog.org>
> Sent: Tuesday, June 12, 2007 12:43 PM
> Subject: Re: gre on PPPoE
>
>
>> On Tue, Jun 12, 2007 at 12:04:58PM +0300,
>> Siwangu Mgata <svmgata at sihebs.co.tz> wrote
>> a message of 72 lines which said:
>>
>>> I want to run a data store application between these two offices but
>>> the challenge is when i create a VPN, the application stop working.
>>
>> Can you give more details? For instance, does the application work
>> between the two sites when *not* using a VPN, just a regular IP link?
>>
>> (If so, I would suspect a TCP MSS problem, triggered by the lower MTU
>> of the VPN. If I'm right, the TCP connection will be established but
>> the data transfer will not occur.)
>>
>>> It stop working even when i create a simple ipip tunnel
>>
>> Same remark. More details are welcome. A simple tcpdump may
>> suffice. Pinging the IP addresses also (a "data store application" is
>> a terrible debugging tool).
>>
>>
>
>
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