Add proxy arp on Checkpoint SPLAT

When doing client side NAT’ing on Checkpoint boxes and using manual NAT creations the process differs between platforms.

IPSO is probably the most straight forward:

1. Ensure you have the NAT rule in the policy
2. Go to Voyager; add a proxy arp entry

But on SPLAT I found I had to do the following;

1. Ensure you have the NAT rule in the policy
2. In Dashboard; Global Properties / NAT / Untick ‘Automatic ARP configuration’ – install policy if necessary
3. SSH to device and enter expert mode
4. cd $FWDIR/conf ; vi local.arp
5. Add a line with your IP and interface MAC address in the format: 123.123.123.123   AA:BB:CC:DD:EE:FF
6. Save file
7. Apply the config by restarting Checkpoint; $host>cpstop && cpstart (Thanks @Levente Szabo for the update)

Only now would the device respond to arp requests for that IP address – ie when creating manual NAT.