Server NAT crashed after install server.app 2.1 in OSX 10.8.2

I have a server (mac mini) OSX 10.8.2. It was working with DHCP and NAT activated manually (command line) but after update it, service NAT do not work. I followed all steps that show here http://support.apple.com/kb/HT5215 without success. I have 2 interfaces: en0 connected to internet and en3 to LAN.

Someone has an idea thanks