Have you created a 'local network' on your SME to tell it to route 10.0.0.0/24 through 192.168.55.251?
When you access your SME from your local network, does the traffic originate from 10.0.0.x or from 192.168.55.251? That is, is your Linksys still doing NAT? If so, you won't get anything back through the Linksys from the WAN side with out:
- turning off NAT (set 'router' mode?)
- creating port forwarding rules
- setting up a 10.0.0.x host as the 'DMZ' on the Linksys.
It's a lot easier if you get a WAP54G instead...