what i learnt today - Tag - mtuRandom crap that I learn. No particular topic. Anything I feel I want to post and have the motivation to post, will be posted.2015-08-15T10:48:18+10:00fukawi2urn:md5:a865e0fca55289dd0bb01a2a26e97267DotclearOpenVPN MTU Sizeurn:md5:36b424927a43182dc7aaee045662800b2009-01-08T09:34:00+11:002009-01-28T16:47:14+11:00PhilLinux & Open Sourcelinuxmtuopenvpn<p>I came across a problem recently while attempting to transfer a largish (23mb) file from my web server to my file server via my OpenVPN tunnel.</p>
<p>The tunnel has been working perfectly since it was first established. SSH and small file copies went fine. But this copy would get to 2,112kb and then stall. No matter how many times I attempted it. I attempted the same transfer using the public interwebs (I was scp'ing so it was encrypted anyway) and this worked perfectly, so there was obviously a problem with the OpenVPN tunnel.</p> <p>Doing a tcpdump on both ends, and the firewall where the tunnel terminates showed that the traffic would flow freely up to the 2,112kb mark, then you could see packets entering the tunnel at the web server end, but not exiting at the firewall end.
A quick Google and scan through the OpenVPN book pointed at using this command to test the maximum... <a href="http://www.wandin.net/dotclear/index.php?post/2009/01/08/OpenVPN-MTU-Size"><em>Read</em> OpenVPN MTU Size</a></p>