Red Hat Bugzilla – Bug 486113
Default MTU value too Large
Last modified: 2009-12-18 02:57:19 EST
Description of problem:
The MTU value of 1412 causes traffic over the VPN tunnel to
"freeze" at some locations.
Version-Release number of selected component (if applicable):
Works every time at a location where the ISP has a lower MTU setting.
Steps to Reproduce:
1. Establish VPN Connection
2. Try any kind of network activity (ssh / http / dns)
3. See connection hang and timeout
4. VPN connection does not get disconnected
Fix MTU value (to 1390)... problem is resolved. Ubuntu
seems to have this hardcoded in /etc/vpnc/vpnc-script
data transfer hangs.
data transfer works.
From: Giray Devlet <firstname.lastname@example.org>
Reply-to: vpnc list to send bug reports and discussions with developers <email@example.com>
To: Francois Cami <firstname.lastname@example.org>
Cc: vpnc list to send bug reports and discussions with developers <email@example.com>
Subject: Re: [vpnc-devel] ssh freezing
Date: Wed, 18 Feb 2009 15:26:29 +0100
Mailer: Evolution 2.24.3 (2.24.3-1.fc10)
Thank you ... Interestingly enough everyone claims not to have changed anything, but the MTU
setting indeed solved the issue.
On fedora setting MTU from "MTU=1412" to "MTU=1390" in /etc/vpnc/vpnc- script
The ubuntu boxes seem to have it in it already ...
On Tue, 2009-02-17 at 17:03 +0100, Francois Cami wrote:
> That looks like a MTU/PMTUD problem.
> Are you blocking ICMP type 3 at the problematic site ?
> 2009/2/17 Giray Devlet <firstname.lastname@example.org>:
> > Hi,
> > I have an interesting problem ... two seperate Fedora 10 boxes, one with
> > Fedora 8, and one
> > Ubuntu box. Location 'B' has a Fedora 10 box
> > All with vpnc 0.5.3 and similiar installations. They all connect to Cisco
> > VPN 3000 boxes ... (two seperate boxes
> > in two seperate data centers)
> > The two Fedora boxes in Location A, connect but ssh connections "freeze"
> > after a bit of data
> > has flown ... (think 'ls'). The rest of the boxes do not have this issue. I
> > however am able to login, and
> > logout ... or when the ssh is frozen open up login from another terminal via
> > ssh.
> > It also does not seem to be only SSH but any data connection (did a telnet
> > on port 80 and then a GET /)
> > The issue seems very location specific, since I cannot replicate the issue
> > anywhere else.
> > Am open to any suggestion, any way to debug the problem ...
> > tia
> > [root@puma ~]# vpnc --version
> > vpnc version 0.5.3
> > Copyright (C) 2002-2006 Geoffrey Keating, Maurice Massar, others
> > vpnc comes with NO WARRANTY, to the extent permitted by law.
> > You may redistribute copies of vpnc under the terms of the GNU General
> > Public License. For more information about these matters, see the files
> > named COPYING.
> > Built without openssl (certificate) support.
> > Supported DH-Groups: nopfs dh1 dh2 dh5
> > Supported Hash-Methods: md5 sha1
> > Supported Encryptions: null des 3des aes128 aes192 aes256
> > Supported Auth-Methods: psk psk+xauth
> > [root@puma ~]#
> > Best Regards,
> > Giray
> > _______________________________________________
> > vpnc-devel mailing list
> > email@example.com
> > https://lists.unix-ag.uni-kl.de/mailman/listinfo/vpnc-devel
> > http://www.unix-ag.uni-kl.de/~massar/vpnc/
Editing /etc/vpnc/vpnc-script has no effect on NetworkManager
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