Apparently, a router client lease time expiring disrupts a SSH connection.
True or false?

If false, it's a one in a thousand coincidence.
--
rhhardin@mindspring.com

On the internet, nobody knows you're a jerk.

On 2007-08-26, Ron Hardin <rhhardin@mindspring.com> wrote:
> Apparently, a router client lease time expiring disrupts a SSH connection.
> True or false?

Well, it depends: if the leased ip address changes, then the SSH
connection will be lost.

If the ip address doesn't change, then there's no reason the SSH
connection should be interrupted, unless the client router is so badly
implemented that it resets its connection table when it re-leases.

> If false, it's a one in a thousand coincidence.

Does it happen every time the lease expires?

> On the internet, nobody knows you're a jerk.

Actually, in my experience, it generally doesn't take more than a
couple of postings to tell who the jerks are...

Ron Hardin <rhhardin@mindspring.com> wrote:
> Apparently, a router client lease time expiring disrupts a SSH connection.
> True or false?

Well if it actually *expires*, then I'd imagine that means that the
lease could not be renewed, otherwise the client would have done so
beforehand.

That suggests that the original IP address was no longer valid and was
released by the client. If the SSH connection was using that IP
address, then yes the connection (or any other using it) would have been
disrupted.

--
Darren Dunham ddunham@taos.com
Senior Technical Consultant TAOS http://www.taos.com/
Got some Dr Pepper? San Francisco, CA bay area
< This line left intentionally blank to confuse you. >

Ron Hardin <rhhardin@mindspring.com> wrote:
> Apparently, a router client lease time expiring disrupts a SSH connection.
> True or false?

Well if it actually *expires*, then I'd imagine that means that the
lease could not be renewed, otherwise the client would have done so
beforehand.

That suggests that the original IP address was no longer valid and was
released by the client. If the SSH connection was using that IP
address, then yes the connection (or any other using it) would have been
disrupted.

--
Darren Dunham ddunham@taos.com
Senior Technical Consultant TAOS http://www.taos.com/
Got some Dr Pepper? San Francisco, CA bay area
< This line left intentionally blank to confuse you. >

On 2007-08-26, Ron Hardin <rhhardin@mindspring.com> wrote:
> Apparently, a router client lease time expiring disrupts a SSH connection.
> True or false?

In the general case, false. Windows, however, seems to like killing
connections when it renews DHCP leases, usually at 1/2 the least time
(happened to me with XP, not sure about other versions).

On the other hand my OpenBSD laptop has SSH sessions that have been
running for a week or more (on a 24hr DHCP lease).

--
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4 37C9 C982 80C7 8FF4 FA69
Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

On 2007-08-26, Ron Hardin <rhhardin@mindspring.com> wrote:
> Apparently, a router client lease time expiring disrupts a SSH connection.
> True or false?

In the general case, false. Windows, however, seems to like killing
connections when it renews DHCP leases, usually at 1/2 the least time
(happened to me with XP, not sure about other versions).

On the other hand my OpenBSD laptop has SSH sessions that have been
running for a week or more (on a 24hr DHCP lease).

--
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4 37C9 C982 80C7 8FF4 FA69
Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

Darren Dunham wrote:
>
> Ron Hardin <rhhardin@mindspring.com> wrote:
> > Apparently, a router client lease time expiring disrupts a SSH connection.
> > True or false?
>
> Well if it actually *expires*, then I'd imagine that means that the
> lease could not be renewed, otherwise the client would have done so
> beforehand.
>
> That suggests that the original IP address was no longer valid and was
> released by the client. If the SSH connection was using that IP
> address, then yes the connection (or any other using it) would have been
> disrupted.

Well, it's on XP Home running a Putty SSH keep-alive window that sends back
the time around once a minute. After the connection was lost we find on XP

$ ipconfig -all
....
Lease Obtained. . . . . . . . . . : Sunday, August 26, 2007 4:51:58 PM
Lease Expires . . . . . . . . . . : Monday, August 27, 2007 4:51:58 PM

and in the XP SSH window used to keep the line up by appearing to use it

.... [many hours of unix date command output] ...
Sun Aug 26 16:40:28 EDT 2007
Sun Aug 26 16:41:48 EDT 2007
Sun Aug 26 16:42:51 EDT 2007
Sun Aug 26 16:43:44 EDT 2007
Sun Aug 26 16:45:03 EDT 2007
Sun Aug 26 16:45:54 EDT 2007
Sun Aug 26 16:47:06 EDT 2007
Sun Aug 26 16:48:00 EDT 2007
Sun Aug 26 16:49:05 EDT 2007
Sun Aug 26 16:50:15 EDT 2007
Sun Aug 26 16:51:12 EDT 2007

and the putty window then says that server unexpectedly dropped the connection.

Notice the output ends when the new lease was acquired. Too much of a coincidence.

I imagine though that it kept the same IP address, there being no contending system
and it already having the lowest address.

I thought perhaps there's a session number of something that does change when the
connection renews, but who knows.

--
rhhardin@mindspring.com

On the internet, nobody knows you're a jerk.

Darren Dunham wrote:
>
> Ron Hardin <rhhardin@mindspring.com> wrote:
> > Apparently, a router client lease time expiring disrupts a SSH connection.
> > True or false?
>
> Well if it actually *expires*, then I'd imagine that means that the
> lease could not be renewed, otherwise the client would have done so
> beforehand.
>
> That suggests that the original IP address was no longer valid and was
> released by the client. If the SSH connection was using that IP
> address, then yes the connection (or any other using it) would have been
> disrupted.

Well, it's on XP Home running a Putty SSH keep-alive window that sends back
the time around once a minute. After the connection was lost we find on XP

$ ipconfig -all
....
Lease Obtained. . . . . . . . . . : Sunday, August 26, 2007 4:51:58 PM
Lease Expires . . . . . . . . . . : Monday, August 27, 2007 4:51:58 PM

and in the XP SSH window used to keep the line up by appearing to use it

.... [many hours of unix date command output] ...
Sun Aug 26 16:40:28 EDT 2007
Sun Aug 26 16:41:48 EDT 2007
Sun Aug 26 16:42:51 EDT 2007
Sun Aug 26 16:43:44 EDT 2007
Sun Aug 26 16:45:03 EDT 2007
Sun Aug 26 16:45:54 EDT 2007
Sun Aug 26 16:47:06 EDT 2007
Sun Aug 26 16:48:00 EDT 2007
Sun Aug 26 16:49:05 EDT 2007
Sun Aug 26 16:50:15 EDT 2007
Sun Aug 26 16:51:12 EDT 2007

and the putty window then says that server unexpectedly dropped the connection.

Notice the output ends when the new lease was acquired. Too much of a coincidence.

I imagine though that it kept the same IP address, there being no contending system
and it already having the lowest address.

I thought perhaps there's a session number of something that does change when the
connection renews, but who knows.

--
rhhardin@mindspring.com

On the internet, nobody knows you're a jerk.

Ron Hardin <rhhardin@mindspring.com> wrote:

> Notice the output ends when the new lease was acquired. Too much of a
> coincidence.
>
> I imagine though that it kept the same IP address, there being no
> contending system and it already having the lowest address.
>
> I thought perhaps there's a session number of something that does
> change when the connection renews, but who knows.

In my experience, windows systems drop established connections very
quickly (instantly?) if the network is reset. I do not think it normal
for a network reset to accompany a dhcp renewal.

My current (XP) computer is sitting on a network with 2 hour leases, and
the ssh windows on in have been up for about a week. So they've likely
survived close to 200 renewals at this point (presumably no expirations,
though).

--
Darren Dunham ddunham@taos.com
Senior Technical Consultant TAOS http://www.taos.com/
Got some Dr Pepper? San Francisco, CA bay area
< This line left intentionally blank to confuse you. >

Ron Hardin <rhhardin@mindspring.com> wrote:

> Notice the output ends when the new lease was acquired. Too much of a
> coincidence.
>
> I imagine though that it kept the same IP address, there being no
> contending system and it already having the lowest address.
>
> I thought perhaps there's a session number of something that does
> change when the connection renews, but who knows.

In my experience, windows systems drop established connections very
quickly (instantly?) if the network is reset. I do not think it normal
for a network reset to accompany a dhcp renewal.

My current (XP) computer is sitting on a network with 2 hour leases, and
the ssh windows on in have been up for about a week. So they've likely
survived close to 200 renewals at this point (presumably no expirations,
though).

--
Darren Dunham ddunham@taos.com
Senior Technical Consultant TAOS http://www.taos.com/
Got some Dr Pepper? San Francisco, CA bay area
< This line left intentionally blank to confuse you. >