On Thu, Sep 02, 2010 at 04:55:32PM +0800, eric li wrote:
> Hi,all
> 
>    I have a problem when use LVS:
> 
>         director use Tunnel Mode
>         a UDP server running on the realserver
> 
>   when client send UDP requests to lvs, it can not receive the realserver's
> response.
> 
> 
>   I capture packets on the director using ethereal, the packet shows that:
> 
>        director receives the  requests , but dose not transmit then to
> realserver
>        the requests size is 1464(not include the UDP and IP header)
>        the IP header set the DON'T FRAGMENT to 1
> 
> 
> i guess the reason is like that:
> 
>         requests size is 1464 and plus UDP and IP header will become 1492.
> when director add a IP header on it,its size will be 1512, which exceeds the
> MTU(1500). Because the IP header set the DON'T FRAGMENT to 1, director only
> have to drop the packets.
> 
> 
> Can anynoe tell me why ?
> 
> Why the  the IP header's DON'T FRAGMENT  flag is 1?

Hi Eric,

off-hand I don't have an answer for that.
But could you try manually reducing the MTU on the client
to see if that helps?


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