I have a NAS set up that I need to work on 2 different subnets. It works perfectly when only connected on eth0 (i.e. reachable from all subnets) but when I bring up eth1 suddenly eth0 is only accessible from inside it's subnet. eth0 is not behind a router and gets an ip of x.x.108.x and eth1 is connected to a router (router ip: x.x.172.x) with an internal IP of 10.0.0.5. I have ssh smb and ftp on the NAS, none of which are accessible from outside the 108 or internal router subnet when both interfaces are up. The NAS is running ubuntu 9.10 with nothing major modified, just X killed and wpa_supplicant set to authenticate PEAP/MSCHAPv2 on eth0 on boot. The default route is x.x.108.1

Do you know that ubuntu 9.10 appeared on October 26, 2009, less then month ago, and still buggy.

How did you configure NAS interfaces? Manually or through NM or WICD?

IP settings are all done with dhclient and wpa_supplicant through the terminal. I had openfiler on it at first, which weirdly did the exact same thing (blocking outside subnet access) but didn't support HFS+ through the web interface (2 of the drives are HFS+) so I figured I'd just go for something with an up to date kernel and the ability to install packages from the terminal.

Excuse me, your NAS is in LAN, and all interfaces eth0 and eth1 connected to router, why do you use dhsp, why not to set up them manually and what is wpa_supplicant doing there?

Sorry, may be I've missed something.

eth1 is going to a router that is set up for DHCP (like most routers are), thus the need for dhclient. The router is connected to the external network on subnet 172.
eth0 is not going to the router, it's going to the outside network which requires 802.1x authentication (which wpa_supplicant does). I have the authentication set up and working, eth0 is on subnet 108.