Löwe schrieb:Problem gelöst, vielen Dank oc2pus!
Ich habe die erste genannte Befehlskette eingegeben:
# iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
Nun funzt es tadellos........bitte sei nicht mehr böse, es war echt nur ein schlampiger Irrtum.
Lieben Dank nochmals jetzt hab ich auch wieder Motivation weiter zu machen mit Linux.....
zero0109 schrieb:Ich habe das selbe Problem, das Dumme ist nur, dass ich den oben genannten Link nicht aufrufen kann. Kann mir vielleicht irgend jemand den relevanten Inhalt der Seite zitieren?
15.7. Circumventing Path MTU Discovery issues with MSS Clamping (for ADSL, cable, PPPoE & PPtP users)
As explained above, Path MTU Discovery doesn't work as well as it should anymore. If you know for a fact that a hop somewhere in your network has a limited (<1500) MTU, you cannot rely on PMTU Discovery finding this out.
Besides MTU, there is yet another way to set the maximum packet size, the so called Maximum Segment Size. This is a field in the TCP Options part of a SYN packet.
Recent Linux kernels, and a few PPPoE drivers (notably, the excellent Roaring Penguin one), feature the possibility to 'clamp the MSS'.
The good thing about this is that by setting the MSS value, you are telling the remote side unequivocally 'do not ever try to send me packets bigger than this value'. No ICMP traffic is needed to get this to work.
The bad thing is that it's an obvious hack - it breaks 'end to end' by modifying packets. Having said that, we use this trick in many places and it works like a charm.
In order for this to work you need at least iptables-1.2.1a and Linux 2.4.3 or higher. The basic command line is:
# iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
This calculates the proper MSS for your link. If you are feeling brave, or think that you know best, you can also do something like this:
# iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 128
This sets the MSS of passing SYN packets to 128. Use this if you have VoIP with tiny packets, and huge http packets which are causing chopping in your voice calls.
zero0109 schrieb:So jetzt habe ich die beiden mal probiert, gebracht hats leider garnichts.