Network isolation?

[Karl Auer]

On Sat, 2022-03-05 at 18:02 -0800, MR ZenWiz wrote:
> <on desktop> ping <laptop> - succeeds
> <on desktop> ssh <laptop> - succeeds.
> <on laptop> ping <desktop> - fails ("Destination Host Unreachable")
> <on laptop> ssh <desktop> - fails ("No route to host")

Sorry, coming in late here, apologies if this ground has been covered.

This sounds like a routing problem. It looks as if the desktop has a
route for your local network, but the laptop does not. Assuming you
don't have weirdnesses (like a VPN running on the laptop), do this on
both systems:

ip route

And post the results. If the laptop is Windows, it's "route print" I
think.

This is normal for my Linux laptop:
kauer at kt1:~$ ip route
default via 192.168.1.1 dev eth0 proto dhcp metric 100
192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.254
metric 100

The first line sends all traffic to the router, unless there is a more
specific route for it. The second line is a more specific route that
sends all traffic for my local network out eth0.

Without the second line, all traffic from my laptop would go to the
router.

I can't say why or how your laptop might have lost its local route, but
it does look a bit like that.

If you ARE missing a local route on the laptop (and it's Linux, I have
no ide how to add a route in Windows), you could try adding it back
like this (substitute your local network address for "192.168.1.0/24"
and your interface address for "192.168.1.254"):

sudo ip route add 192.168.1.0/24 dev eth0 proto kernel scope link src
192.168.1.254 metric 100

If everything starts working, you then have to figure out why that
route went away. Obviously reboot the laptop before you do anything
else. Even better, power cycle it.

Regards, K.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Karl Auer (kauer at biplane.com.au)
http://www.biplane.com.au/kauer

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