Re: strange TCP problem looks like PMTU but isn't
On Thursday, 28 April 2016 10:46:31 AM AEST Russell Coker via luv-main wrote: > but "ping -M want -s 1400 8.8.8.8" works without any problems I usually use "-M do" for that sort of testing. The "tracepath" program will also show you the MTU along the route (as long as UDP isn't being blocked). ...and from bitter experience I would suggest doing the same test in the reverse direction; at work we were having problems for a while with sites outside using jumbo frames until we learnt that the uni had asymetric routing and the return path had a different MTUon one segment to the incoming path. Oh, and some bright spark had decided that they could save IP's by using RFC1918 addresses on those segments and so the router was sending out PMTUD ICMP's with addresses that would get dropped at the border. :-/ Good luck! Chris -- Chris Samuel : http://www.csamuel.org/ : Melbourne, VIC ___ luv-main mailing list luv-main@luv.asn.au https://lists.luv.asn.au/cgi-bin/mailman/listinfo/luv-main
Re: strange TCP problem looks like PMTU but isn't
On Thu, Apr 28, 2016 at 10:46:31AM +1000, luv-main wrote: > I've got a Linux system running remotely that has a strange TCP problem, when > it sends (not receives) a large packet the connection hangs. For example if I > ssh in and run commands with small amounts of output everything is fine, but > if > I run "ls -l /" then the connection hangs forever. > > My first thought was PMTU discovery, but "ping -M want -s 1400 8.8.8.8" works > without any problems and also setting the MTU on the only Ethernet device to > unusually low values (I tried as low as 400 bytes) didn't make any difference. > > Any ideas as to what I should try next? > > The system in question is a fairly standard AMD64 desktop PC running > Debian/Jessie. > Start a tcpdump to a file before issue ls -l. Suspect you will see packet not being acknowledged, likely due to faulty hardware somewhere. Cheers ... Duncan. ___ luv-main mailing list luv-main@luv.asn.au https://lists.luv.asn.au/cgi-bin/mailman/listinfo/luv-main
