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You've got a buggy router
Authored by: ducasi on Jun 16, '04 06:07:15PM

This must be the result of a buggy router.

Routers should not time out connections after 10 minutes when it knows fine that the connection is still open. OpenSSH normally tickles the connection every 30 minutes using a TCP keep-alive packet (a 0-byte packet.) This is a TCP standard. If the router drops the connection sooner than that it's not keeping to the standard.

I used to use a NetGear router that dropped TCP keep-alives. As a result my TCP sessions would die maybe an hour after being idle. (It doesn't mind losing one keep-alive, but gets upset if two go missing.)

As a result I had to turn on these ClientAlive tickles. I also decided to dump the router.



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You've got a buggy router
Authored by: drauh on Jun 17, '04 12:01:24AM

What router did you get, instead?



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You've got a buggy router
Authored by: n9yty on Jun 17, '04 12:37:22AM

Not a buggy router...

This isn't necessarily a ROUTER issue, so much as a NAT issue. The system decides which NAT'd connections to track, and if they aren't used after a period of time, they drop out. This even happenened in some of the earliest Linux setups I put together using ipmasq to provide NAT services... You could specify the timeout differently for various services if you wish, but most "cheap" routers/etc don't offer you that.



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You've got a buggy router
Authored by: napdaddy on Jun 17, '04 04:52:23PM

Maybe this explains why I always seem to lose my Cisco VPN connection at home after short periods of inactivity. If I'm at work, I can keep the VPN connection up indefinitely without doing anything. I have a Netgear WGR614 at home. Maybe that's the culprit. Any suggestions to fix this short of getting a new router would be welcome. Any suggestions for a new router would be welcome too. :)

disclaimer: I'm running the Cisco VPN client on my win2k machine, but it's pretty much the same deal.



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You've got a buggy router
Authored by: bill_mcgonigle on Jun 17, '04 08:29:35PM

Technically, it's a bug. But NAT vendors bill it as a feature.

Most customers don't know this feature is on or where to turn it off or that it's usually set for 5-10 minutes by default.

And you can't control all the NAT gateways between your home and your destination, typically.

Hence the SSH guys came through with a fix. FYI, setting TCP SO_KEEPALIVE doesn't make these NAT boxes work, they ignore it.



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You've got a buggy router
Authored by: jporten on Jun 18, '04 07:10:55PM

The network you're using is somehow also involved. I'm using a first-gen Airport at home. At home, SSH connections persist however long (I've got one that's been running, mostly unused, for 16 hours). Other places, they drop after a few minutes idling.

I narrowed this down to connections coming in over T-Mobile hotspots; will see if this fix helps at all.



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