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Re: Access to sub network unreachable.



On Fri, 2009-01-09 at 11:58 -0800, Rick Stevens wrote:
> Robin Laing wrote:
> > Simon Slater wrote:
> >>     Hi all,
> >>         I'm sure I have missed something simple (or done something 
> >> stupid) but
> >> have no idea what so I'll ask anyhow.
> >>
> >>     All the computers on our SOHO network had static addresses in the
> >> 192.168.0.1-9 range with netmask of 255.255.255.0 and all worked fine
> >> for ages.  Now I have a Linksys gateway which has a default address of
> >> 192.168.1.1 for configuration.  It works fine as a DSL router but I
> >> cannot use a browser to access the configuration.  All I get is "An
> >> error occurred while loading http://192.168.1.1: Could not connect to
> >> host."  Pinging returns "Destination Host Unreachable".
> >>
> >>     I changed the netmask for the ethx device to 255.255.0.0 but this 
> >> made
> >> no difference.  What have I forgotten?
> 
> Odds are that the router also has a netmask of 255.255.255.0 (or a /24).
> If that's the case, then it can't talk to your client since your client 
> isn't on the router's LAN as far as the router is concerned.  Your
> client can talk to the router with a /16, but the router can't reply to
> you as it'd try to talk to you over its WAN port.  Options:
> 
> 1. Change all of your client machines to 192.168.1.xxx with netmasks of
> 255.255.255.0 (/24) to conform to the router's defaults, or
> 
> 2. Change the netmask on the router to 255.255.0.0 (/16) and all of the
> client machines to the same, or
> 
> 3. Change the IP and netmask of the router to 192.168.0.xxx/24 and leave
> your clients alone.
> 
> I'd vote for number 3...it makes your new router look like the old 
> router.  Remember, though, that if you ever reset your router to the
> factory defaults, you'll need to change its IP again afterward or
> you'll be right back here where you started.  :-)
> 
> How to change it?  On your client:
> 
> 1. # ifconfig eth0 192.168.1.whatever netmask 255.255.255.0
> 2. (browse to 192.168.1.1 and change the IP on the router)
> 3. # ifconfig eth0 192.168.0.whatever netmask 255.255.255.0 (needed
> because your router is now on 192.168.0.0/24)
> 
	Thanks everyone for your replies. I think I know where I went wrong
now: even though the /24 range covers both 192.168.0 and 192.168.1 they
are separate network segments and won't talk to each other.

	I need to read more on addressing and netmasks.  Once our half dozen
boxes were working nicely back in the FC3 days I haven't changed the
setup since (and probably forgot what little I knew about addressing).

	In the next 3 months I'll be adding another half dozen boxes and allow
for laptops so will be setting up DHCP. The F10 download has just
finished, so now I might install that first, then follow your advice to
setup the gateway, then begin experimenting with DHCP.

	Many thanks everyone.

-- 
Hooroo,
Simon
Registered Linux User #463789. Be counted at: http://counter.li.org/



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