On Mon, Mar 04, 2002 at 08:23:06PM +0200, Aviram Jenik wrote: > A question to the MTU gurus (Muli/Dani?):
dani is the real expert, i'm just using a few handy heuristics. > I'm pretty sure I have an MTU problem. However, I can't figure out: > A. How to 'debug' it (i.e. I don't know if the problem is really > MTU) pakcet dump (ethereal, tcpdump). you will see the client sending a packet and getting one packet in a response, or none at all. then it will continue sending and get no response. > B. What the problem is (if it exists). see dani's note, at http://damyen.technion.ac.il/~dani/adsl-mtu.txt > I think that (A) is especially important, since I'm getting the feeling I'm > chasing ghosts; > > The symptoms are as follows: > I'm have an excellent ADSL connection, but connecting to certain servers > using timeout-sensitive protocols I am having problems. For example, when > trying to upload files to my FTP server, either using FTP or SSH + rz, the > connection takes forever and breaks up in the middle quite frequently. > Pinging the server shows that my packet loss is negligible and that the > connection is fast (~35ms, <1% packet loss). Other people can FTP with no > problems. I have no other problems with that server or with my Internet > connection in general (i.e SMTP, HTTP all work quite nicely). The only think > I can think of is some strange MTU problem. that sounds likely, according to the symptoms you describe. does this happen when connecting through the adsl masquerading "server" (the computer which runs pptp) or only when connecting through a masqueraded client? > For example, trying to FTP from my linux connection (the one connected to an > ADSL) via FTP fails miserably with timeouts. The connection is done > directly, so it's not a masquerading problem. > > Now the facts: > The MTU on the ppp0 interface is: 1452 > The MTU on the eth1 interface (the one connected to the ADSL modem) > is: 1500 sounds correct. > as far as I can tell from the how-to, that should be the right values. Any > idea how I can debug it and/or fix the problem? use the ethereal, luke :) -- The ill-formed Orange Fails to satisfy the eye: http://vipe.technion.ac.il/~mulix/ Segmentation fault. http://syscalltrack.sf.net/ ================================================================= To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
