ip routing 'stopped' working

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http://forums.fedoraforum.org – Good day. The system is Fedora 17 used as a router, firewall, and mail. It is connected to the internet via a bridge and all services run directly in the system work correctly. It is able to access all required external services. The internal network is a configured as a subnet with 4 systems connected through a Linksys router. I made some small firewall changes yesterday, however the system worked after those changes. This setup has been working for over a year. I have tried tcpdump trace for a ping from the server that works and see the packets on the external connection. However a ping (HowTos)