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Home > Archive > Linux Debian support > September 2007 > Cannot ssh - network routing problem
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Cannot ssh - network routing problem
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| Geico Caveman 2007-09-19, 7:12 pm |
| Consider three computers A, B and C and three wireless networks - 1, 2 and
3.
A is configured to run a dhcp server over its eth0 interfaces. A dhclient
runs on its wlan interface in wireless network 1. I have no control over
the wireless router in this case (at work).
C is configured to run a dhcp server over its wlan interface, providing
wireless network 2. A dhclient runs on its eth0 interface (directly
connected to a wireless router), that IP address being a part of the IP
address range in wireless network 3 provided by that router. I control this
router (at home).
Openssh servers are installed on A and C. A runs Ubuntu 7.04. B and C run
Debian Testing.
When all the firewalls are down (on A and B, and B and C, and this is
important for later reference - so please do not make any suggestions
regarding firewalls), I get routing errors like :
When in wireless network 1, I try to ssh from B to A, I get :
ssh: connect to host xx.xx.xx.xx port 22: No route to host
Nothing like this happens when I connect B and A via a crossover cable (over
the wired network served by A's dhcp server).
Same thing happens when I try to ssh from B to C on wireless network 3.
Nothing like this happens when I am on wireless network 2.
How do I find out what is going on and why ssh servers on clients in a
wireless network simply do not see incoming packets ? All firewalls are
down, remember ? And ssh servers are working fine by themselves, as seen by
their behaviour when B is a client in their respective network.
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| Rodney 2007-09-20, 1:14 pm |
| On Wed, 19 Sep 2007 11:34:30 -0700, Geico Caveman wrote:
> Consider three computers A, B and C and three wireless networks - 1, 2 and
> 3.
>
> A is configured to run a dhcp server over its eth0 interfaces. A dhclient
> runs on its wlan interface in wireless network 1. I have no control over
> the wireless router in this case (at work).
>
> C is configured to run a dhcp server over its wlan interface, providing
> wireless network 2. A dhclient runs on its eth0 interface (directly
> connected to a wireless router), that IP address being a part of the IP
> address range in wireless network 3 provided by that router. I control
> this router (at home).
>
> Openssh servers are installed on A and C. A runs Ubuntu 7.04. B and C run
> Debian Testing.
>
> When all the firewalls are down (on A and B, and B and C, and this is
> important for later reference - so please do not make any suggestions
> regarding firewalls), I get routing errors like :
>
> When in wireless network 1, I try to ssh from B to A, I get :
>
> ssh: connect to host xx.xx.xx.xx port 22: No route to host
>
> Nothing like this happens when I connect B and A via a crossover cable
> (over the wired network served by A's dhcp server).
>
> Same thing happens when I try to ssh from B to C on wireless network 3.
> Nothing like this happens when I am on wireless network 2.
>
> How do I find out what is going on and why ssh servers on clients in a
> wireless network simply do not see incoming packets ? All firewalls are
> down, remember ? And ssh servers are working fine by themselves, as seen
> by their behaviour when B is a client in their respective network.
Well, your description is fairly complex, this looks like a situation
where a drawing a picture might help you figure it out. Actually, it looks
a lot like a test question. It's certainly not clear to me where B is
getting its IP address in the cases where it fails B to A. From your
description I have no idea if you are trying to ssh to the correct IP
address for C in the case of B to C through network 3. I'd think you might
get some information from the commands ifconfig and route that could help
you sort it out.
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