[Info-vax] invisible vax

[Hans Vlems]

Alain,
As you may have noticed we are all guessing what happened at your place. Your posts are long on text and extremely short on technical information. 
So I add my assumptions (wild guesses).

You wrote 192.168.*.*
Now 192.168.0.0 are 255 networks, each net may have up to 254 systems. This is reflected by the network mask: for these networks that is 255.255.255.0
As others have already written, 192.168.*.* network addresses are never allowed out on the public Internet. Which means that you may combine and use them as one network, using the mask 255.255.0.0
Replacing the router would definitely mess this up since the new one will certainly not be using that short mask.

Because 192.168.*.* addresses may never get out on the Internet they are replaced by your (adsl or otherwise) router.
This is automatically if internet traffic is originated from your LAN.
Looking in from the internet to a system requires translation rules set up on your router. The "outside" address of your router is the only one seen and recognized by the outside public (us).
Your router reads the port number in the header of the UDP/IP or TCP/IP packet, looks it up in a table that you have provided to figure out what the LAN address and port is supposed to be. This method is called NAT or PAT.
An error in this table is easily made.

Another way to direct traffic from the internet to just one node on your LAN is what some routers call a dmz host.
All traffic directed to the outside IP address of your router is passed thru that table, on no match the traffic is sent to the internal IP address that was entered as the DMZ host.

In other words, many ways to introduce problems when exchanging a router.
Hans