Would this work?

[rfbjr]

I couldn't find an existing topic, so here goes.

I have a F2-223 on one home network (1 gig LAN) and the F4-223 on another (2.5gig LAN)

Since I'm only using one NIC on each box, I thought rather than trying to get the two networks to talk to each other on the other NIC (192.168.x & 10.45.x) I would just use a crossover cable on the second NIC and assign each a static IP.

Then in "theory" I should be able to run a backup NAS to NAS.

In my head this sounds plausible even if just down right silly.

Hindsight (yes one home network should have been 192.168.1.x and the other 192.168.2.x and netmask would have done the trick)

[Gremlin]

In my head this sounds plausible even if just down right silly.

Yes

Or VLAN

[rfbjr]

Update: It does work. Crossover cable attached to NIC 2 on both NAS, static IP assigned. Using Duple backup and the vault on the receiving end.
One thing I am checking is the write speed, average 15meg/sec which seems slow. link speed 2.5g and both NAS have 8TB Iron Wolf drives. Source NAS is F2 (Raid 1) and Target is F4 (Raid 5). Need to check if transfer is at half duplex. Bottom line, it does work.