My router shows devices not on the LAN

[bwana]

I have a netgear R7000 that works ok. The network is 192.168.9.0 and the router ip is 192.168.9.9 Recently I attached a NAS via ethernet cable that was from a different LAN and its address is 192.168.7.5 Surprisingly, when i look at attached devices the NAS shows up with its ip address even though it is not addressable on the LAN. Any attempt to find it by using a laptop attached wirelessly to the LAN and logging into it with a browser, or scanning the network is unsuccessful. Same when i try to use an ether net conneccted pc. However I can change the ip address of the pc to 192.168.7.whatever (leaving the gateway blank on the ipv4) and i can open the nas and log into it from a browser. Of course everything else on the LAN is not seen as well as no internet.

Why does the NAS show up in the router but is not 'navigable to' unless i change the ip of the pc? How does the pc 'know' the nas if there is no gateway to negotiate the connection? I am only giving the pc an ip address so how does it know the mac address of the nas to talk to it?

Can I keep the nas with its 'foreign' ip address on the new lan by configuring a static route? (whatever that is-I still do not understand what is going on under the hood of the router when i specify a static route)

 

[ColinTaylor]

Why does the NAS show up in the router but is not 'navigable to' unless i change the ip of the pc? How does the pc 'know' the nas if there is no gateway to negotiate the connection? I am only giving the pc an ip address so how does it know the mac address of the nas to talk to it?

Assuming the NAS is configured with a static IP address (192.168.7.5), when it connects to the network it will announce its IP and MAC addresses via ARP.

Can I keep the nas with its 'foreign' ip address on the new lan by configuring a static route? (whatever that is-I still do not understand what is going on under the hood of the router when i specify a static route)

No. That's not a valid network configuration.

 

[bwana]

Assuming the NAS is configured with a static IP address (192.168.7.5), when it connects to the network it will announce its IP and MAC addresses via ARP.

No. That's not a valid network configuration.

thanks . it's interesting that a router will display ip addresses announced that are not on its network.

 

[dosborne]

it's interesting that a router will display ip addresses announced that are not on its network.

They are on the same PHYSICAL network. If you changed the IP addresses on your PC to be in the same subnet as the NAS, you would be able to access it.