On Sun, 14 Jun 2015 10:41:18 +0200 <email@example.com> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On Sun, Jun 14, 2015 at 12:51:14PM +1000, Riley Baird wrote: > > Hi, > > > > Many of my connections are timing out. For example, I can't use SMTP to > > send a message if it's over ~1500 bytes [...] > > This sounds suspiciously as if your box were using an MTU which is too > big for the path (1500 is about the Ethernet MTU. Perhaps along the path > there is a link with a smaller MTU (typically something encapsulating > the packets, which needs some room for headers, so the available payload > per packet schrinks accordingly). > > In the Good Old Days, your box would get an ICMP reply from the router > in-between by this router, telling that the MTU is too big, but these > days, over-eager firewalls tend to filter out these things. > > Try to reduce the MTU of your interface, with something along the lines > of > > sudo ifconfig eth0 mtu 1400 > > (of course, you'd have to replace eth0 by the real name of your interface. > Just come back here if you don't know what I'm babbling about :-) > > If that works, we can talk about how to make this change more permanent. This works! I'd recently switched from wicd to /etc/network/interfaces, and I didn't realise that I needed to set the MTU manually. I've also found out how to make the change persistent (adding the line "mtu 1400" to /etc/network/interfaces). Thanks for your help; now I can use the internet normally again!
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