2 nics in same subnet - howto?

[UbuntuBantu]

I've got a (probably dumb) question but as I'm no networking guru, I'll ask it anyway.

I have 2 x PCs and a NAS. Both PCs have 2x NICS. PC connectivity to Internet is via an ADSL router.

Current config:
Thus far (by choice) I've used static IPs in the 192.168.168.x range for my internal network, connecting all PCs and NAS via a jumbo frame enabled gigabit switch. This has facilitated moving data between the PCs and the NAS at high-speed.

As both PCs also required Internet access from time to time, both are also connected to the ADSL router using the 2nd NIC and using subnet 192.168.1.x. I'm sure some of you are shaking your heads by now, but it works well and has been entirely hassle free.

Needs:
However, I've an app running on the NAS that I'm keen to get Internet connected also.

My initial gameplan:
As my existing network devices are not using DHCP I figured the simplest method would be to change my ADSL router configuration such that it is in the same 192.168.168.x subnet, change its DHCP server settings to serve IPs in the same subnet (but in a restricted range I know won't cause any conflicts with the static IPs) and problem solved. On changing the ADSL router confiruration with all machines already booted up and configured as described above, everything worked. All devices could see one another, and access the Internet.

On later rebooting the system this no longer works - Internet access is fine but PCs don't see one another or the NAS. If I disconnect the ADSL Router from the PCs then all devices see one another again.

So, a few questions:
- Does having 2x NICS on a single device each assigned unique IPs in the same subnet create an issue and can it be overcome? I'd like to overcome it because making one of my PCs the gateway forces me to have it on anytime another device needs access.
- If I'm forced to use Internet connection sharing with one PC on the network connected to the router, how do I best configure this?
- One of the things I need to retain is gigabit connectivity between the PCs and PCs and the NAS (currently achieved by 192.168.168.x subnet being linked via gigabit switch).

[folkert]

- Does having 2x NICS on a single device each assigned unique IPs in the same subnet create an issue and can it be overcome? I'd like to overcome it because making one of my PCs the gateway forces me to have it on anytime another device needs access.

I don't know, are they both connected to the same switch?

- If I'm forced to use Internet connection sharing with one PC on the network connected to the router, how do I best configure this?

I once used shorewall and it worked.

- One of the things I need to retain is gigabit connectivity between the PCs and PCs and the NAS (currently achieved by 192.168.168.x subnet being linked via gigabit switch).

I would use one nic on each, and connect all: pc1, pc2, router and nas to the gigabit switch. I believe the switch should be so smart to transfer at gigabit speed if the data is not going to the router.

[UbuntuBantu]

I don't know, are they both connected to the same switch?

No. 1 NIC on each Pc is connected directly to my ADSL router. The other NIC is connected to a switch serving the 192.168.168.x subnet.

I would use one nic on each, and connect all: pc1, pc2, router and nas to the gigabit switch. I believe the switch should be so smart to transfer at gigabit speed if the data is not going to the router.

I tried that, doesn't work - either you get access to the PCs or you get internet access, not both.

[folkert]

either you get access to the PCs or you get internet access, not both.

Maybe you need to add the "route" to your router (and the internet), or use the dhcp of your router to get it.

[techwise]

Wow, too much complication going on here. Keep it simple:

one nic in each pc only. or just activate only one.
address all the pcs and nas on the same subnet as the lan side of the router "192.168.1.x"

plug all pcs and nas into the switch

plug the router into the switch from one of its lan ports

Make sure you hard reboot the switch so it starts with empty tables.

Thats it.