puTTY SSH connections dropping when on wifi instead of ethernet

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I use puTTY to create SSH tunnel connections to servers, and usually have the connection up all day. Recently I’ve been plagued with puTTY losing the connection every 15 or 20 minutes – all because I moved to wifi instead of a wired connection. It’s because I bought a new MacBook Pro, which doesn’t have a standard ethernet port, a small fact I didn’t realise so I didn’t buy an adaptor. Plus my family was probably becoming a little bored with the blue network cable hanging down the stairs from our cable router to my study – makes the place look untidy.

I already had keep alives configured in puTTY:

Screen Shot 2013-11-06 at 9.19.46 AM

After some research I came across this post ‘Why Windows 7 / PuTTY drop TCP connections even on very brief outages?‘ which seemed to mirror my own experience to some extent.

I took a look at my Windows registry, and did not see the TcpMaxDataRetransmissions parameter, so added it in with a value of 15 (the superuser post suggests 15, the linked FAQ on the puTTY web site says 10).

2013-11-06_09-22-55

With this change my connection remained up for a couple of hours, and then died, a darn sight better than the previous habit of dropping a couple of times every hour – except this time puTTY doesn’t report the connection as dropped, it looks fine, I just can’t reach anything at the other end of the tunnel.

I decided to fiddle with the puTTY keepalive, and changed it from 30 seconds to 15 seconds, over the past day or two I’m seeing 3 or 4 hours uptime. Interestingly, I only notice when I try to connect to a server and receive a timeout message, previously puTTY would say it was disconnected, now it seems to think the session is still current.

All in all good progress. When I have some time I’ll play with the configuration some more. I haven’t even got to looking at whether there is a setting on my  wifi router that might be to blame.

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