Can some one suggest a firewall setup for a OSPF routed ring network? I feel like it would be a bad idea to have the same router running OSPF be the WAN firewall. Would it be best to put a security appliance on the WAN and then create static route to all the subnets on the OSPF network?
drop all - accept what you want is a good firewall. 
ospf have nothing to “say” it all depends on what you run behind
Is it recommend to have the same router running OSPF also connected to the WAN interface or have a security appliance that connected to one of the OSPF routers?