MAC addresses, hostnames, and DHCP

Ben Scott dragonhawk at gmail.com
Fri Dec 2 11:50:01 EST 2005


On 12/1/05, Paul Lussier <p.lussier at comcast.net> wrote:
>> So you can unplug from Ethernet and go Wireless and not loose your SSH
>> connections (for one).
>
> It's not going to work that well ...

  It should work *if* the SSH connection remains idle during the
transition *and* the TCP sockets are not bound to a particular
interface.  Since IP is stateless (remember *that* thread? ;-) ),
higher layers shouldn't notice if an intermediate link goes away.

  However, there are some caveats.  If any traffic occurs (payload, or
SSH control traffic like rekeying, keep-alive, etc.), TCP (or higher
level protocols) may time out before the IP layer finishes coming back
up.  This is especially likely if you're using SSH to tunnel X11.

  Likewise, if you bind ssh or sshd to a particular interface, when
the interface goes down, the kernel is going to close the TCP socket,
and your SSH session will disappear in a puff of data.

> If you need state on the remote machine maintained, use screen or vnc.

  That's certainly the "right" way to accomplish it.

-- Ben



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