Strange LAN network problem - can't "see" just one address on LAN

[Chris Green]

On Sat, Feb 12, 2022 at 08:30:00PM +0100, Bo Berglund wrote:
> On Sat, 12 Feb 2022 12:30:40 +0000, Chris Green <cl at isbd.net> wrote:
> 
> >On Sat, Feb 12, 2022 at 11:50:55AM +0000, Colin Law wrote:
> >> On Sat, 12 Feb 2022 at 11:47, Chris Green <cl at isbd.net> wrote:
> >> >
> >> > Recently I have been trying out some changes to how the DHCP/DNS is
> >> > managed and, for some strange reason, my desktop machine at
> >> > 192.168.1.3 could no longer 'see' the router at 192.168.1.1.
> >> 
> >> Start by re-booting the router if you have not already done so.
> >> Sometimes they get confused.
> >> 
> >Good advice, it was the router causing the problem though it wasn't
> >that it needed a reboot.  
> >
> >I found that *any* system at 192.168.1.3 couldn't access the router at
> >192.168.1.1.  This made diagnosis much easier because I could
> >configure an unimportant system (as opposed to my mail/ssh server
> >desktop) at 192.168.1.3 and try things.
> >
> >I searched through the router's settings (Draytek Vigor 2860n so there
> >are a *lot* of settings) and I found a 'static route' I'd set while
> >trying to get something else to work.  That static router referred to
> >192.168.1.3 and was why I was getting my strange problem.  I've
> >cleared the setting and all is well now.
> >
> >Phew! :-)
> 
> While you are at it you should *move away altogether* from the local LAN using
> 192.168.1.x or even worse 192.168.0.x addresses!
> Better to use something like 192.168.179.x or similar, or even 10.231.156.x.
> 
> Why? You may ask...
> Well since the IP range you are using is the default for many brands of routers
> including hootels and the like, there are literally millions of LANs out there
> with teh same addresses.
> And you will have a hard time connecting back home using SSH (as you indicated)
> or OpenVPN or similar because if your home LAN is on the same IP range as the
> one you are connected to when calling in there is no way the call will be routed
> through. It just disappears on the local LAN you currently use in the hotel or
> similar....
> 
You said that before! :-)

Connecting back using ssh is totally unaffected by whatever private IP
range my home LAN uses.

I'm never going to use VPNs.

-- 
Chris Green