mpd5.1 MTU problem

Alexander Motin mav at
Thu Jul 17 08:14:31 UTC 2008

Wasily Lin wrote:
>        set iface enable netflow-in
>        set iface enable netflow-out
>        set iface enable ipacct

Strange combination.

>        set iface enable proxy-arp

Are you sure you need it?

>        set iface mtu 1460 <-----------------------!

That's not a problem, but usually 1492 used for PPPoE.
Also in some situation 'set iface enable tcpmssfix' could help.

>    As you can see, tcp/ack from client can not go through but tcp/syn,
> tcp/fin are fine.
> What's the reason? I've used the same client to connect to ISP's ADSL
> and work fine so what I am sure is the server refused my tcp/ack. But why?

As soon as all packets are very small I don't think it is an MTU
problem. I would recommend you to use tcpdump on Ethernet interface to
understand which side actually drops the packets and probably why. Also
check that you are not using any firewall and try to disable some
features on server side like ipacct.

Alexander Motin

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