LAN hosts getting resolved to external NAT address

Luck100

I'm running a number of windows 7 and 8 PCs on a home network, all connected to a UPC horizon router. I seem to have the same problem described here:

http://superuser.com/questions/600369/why-does-my-lan-see-hostnames-as-the-external-nat-address-and-not-the-lan-ip-add

If I do a ping between any two hosts on my LAN, I see the external IP address rather than the LAN address and the pings are slow (100's of milliseconds). If I do a ping with explicit LAN ip addresses, I get 1 ms ping times.

When I try remote desktop connections between hosts on the LAN it fails unless I use the explicit LAN IP address rather than the host name. Presumably this is because the target machine sees the request coming via its external IP address via NAT.

Windows networking between LAN hosts seems to be fine - filesharing works, homegroup works. I double checked and all the hosts are set in windows to obtain IP address and DNS automatically. The UPC horizon router is set to use default DNS settings. I tried google DNS too but that made no difference.

braddun

are you using a windows server

Luck100

no server, just a bunch of pc's running a mix of windows 7 pro, windows 8 pro, and win 7 home.

Luck100

all hosts are connected to the UPC horizon box via wifi or ethernet. no addition routers.

ED E

Don't know how theyve managed to screw their firmware that badly but in any case just de-consolidate from the Horizon box, its a junker.

Luck100

ED E wrote: »

Don't know how theyve managed to screw their firmware that badly but in any case just de-consolidate from the Horizon box, its a junker.

I know the Horizon box is not the greatest but I'm not sure if this is problem with Horizon or something misconfigured on my hosts or network. Does this happen with all horizon boxes? The simple check is to ping another host on your network and see if it comes back with a private or public IP. Or try nslookup for another host.

ED E

With Windows its Netbios/Wins doing all the work. Working normally that will resolve the private address, not the public.

Unless you've set up something funky internally, eg running your own own DNS then it's gotta be the horizon box.

Luck100

Well, I think I've got it figured out. The UPC router has a default domain setting of "net". All my PC's were picking that up and using it as the primary DNS suffix. So when I tried to ping "mypc" it was resolving to "mypc.net", which the router interpreted as a valid internet address (rather than then name of a machine on my lan). So the ping was actually hitting some machine out on the internet called "mypc.net", not my own machine "mypc" on the LAN. Same with remote desktop (which of course failed).

The solution was to just change the domain setting to blank or "local" (or probably anything which isn't a valid internet domain). Then ping, remote desktop, etc work fine on the LAN. As far as I can tell all the name resolution on the LAN happens via NetBIOS, because nslookup still can't find my LAN hosts. I think the horizon box can only forward DNS requests to an external DNS server - it doesn't seem to know the names of the hosts on the LAN (even though it is the DHCP server handing out all the LAN IPs). If you look at the horizon router admin web page, it only shows the IP and MAC address of all the LAN hosts - it doesn't seem to know any names.

Long story short: if you have problems connecting between pcs on your LAN, try changing domain name on the router to "local" or blank. You will need to reboot your pcs for them pick up the name change.

moc moc a moc

Luck100 wrote: »

You will need to reboot your pcs for them pick up the name change.

You can just do an ipconfig /renew, no need to reboot.