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I keep a PuTTY session up on my WinXP laptop all day at work, for tunneling; I also keep the wireless on and, normally, the machine docked (with wired networking). When I dock or undock, and the system thus starts using a different network connection, PuTTY drops the session and I have to start it all over again.

I read that I should try increasing the TCP retries (via setting HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\TcpMaxDataRetransmissions to 20), but this doesn't seem to have helped.

How can I make PuTTY more persistent?

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When you undock you will switch from one LAN interface to another and this is likely to 'win' you a new IP address so the PuTTY session on the now 'dead' one will become abandoned.

If you need to reconnect and carry on with something, check out the screen app

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Hm. This explanation makes sense. But then how does something like, for example, an SQL Server Management Studio session manage to maintain a login across IP-address changes like this? Or, come to that, an ordinary Windows domain login? As for screen, that's cool, but I don't actually do anything in the console, I just have it up for tunneling. The pain of it is that I use a key-with-passphrase SSH login, with, of course, a nice long passphrase for security, as one does. Hey, no problem since I'm only doing this once per day, right right? Whup, not so fast. – Atario Mar 8 '11 at 21:05
@Atario: "ordinary Windows domain logins" are something entirely different; there isn't a long-lasting connection but only a few quick requests and responses to verify your account. – grawity Mar 8 '11 at 21:27
@Atario: PuTTY comes with a SSH key agent named "Pageant". If you load your key into it, you will only need to do it once per day or whatever. – grawity Mar 8 '11 at 21:28
But doesn't this reduce my security by holding on the disk something that's supposed to be a secret in my head? – Atario Mar 8 '11 at 21:34
up vote 0 down vote accepted

My solution was to switch to Bitvise Tunnelier. It appears to cache your credentials, at least till you quit the program or explicitly log out, and attempts reconnection automatically once per minute when the connection is lost. Pretty good on other capabilities, too.

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