Hello,

Question: How does changing the MTU affect the use of rsync?

Background: I have an old PC that I use as a simple ftp server that uses rsync as its backup. Each night it simply syncs it data with my backup server. It currently has an old copy of Mandrake 9.0, before it was Mandriva. I had a friend that had difficulty ftp'ing to my server unless I set the MTU from 1500 to 1443. I believe there is a firewall between us that is complicating the issue. When I changed the MTU he was able to ftp quite well but now my rsync doesn't work. I get the error

"rsync: read error: Connection reset by peer
rsync error: error in rsync protocol data stream (code 12) at io.c"

If I set the MTU back to 1500 rsync works quite happily.
I would have understood if I got less than optimal communication between the ftp and backup server but not nothing. All other means of communication between the two seem just fine. I can ftp, ssh, telnet, rsh, etc. The change in MTU does not seem to have had any great effect on anything but the ftp between my friends system and the ftp server and the rsync between the ftp server and the backup server.

Any help will be greatly appreciated.
Thank you

Unfortunately, some equipment will drop packets that exceed an MTU rather than fragment. It sounds like this is the case for you. Keep your MTU at 1500, and have your friend fix his problem.

Hey, this sound it will solve a problem here.
How do I change the MTU ?
In a 2.6 kernel, IPV6, it is /proc/sys/net/ipv6/conf/eth0/mtu.

How about IPV4 ? How do I change it in a IPV4 network ?

I am having the same problem, I want to try this, but I don't know where to change.

thanks,

The ifconfig command lets you change the mtu on an interface:

ifconfig eth0 mtu 576

"Unfortunately, some equipment will drop packets that exceed an MTU rather than fragment. It sounds like this is the case for you. Keep your MTU at 1500, and have your friend fix his problem."

I thought that might be a problem but was hoping that any switch or router would do the proper fragmenting. Bummer

Thanks I needed the second opinion.