Setting Proxy ARP entries for Manual NATs
From Tech-Wiki
If your recently created manual NAT is not working, maybe you need to create manually proxy ARP entries.
To do so, edit the file $FWDIR/conf/local.arp (or in VSX environments $FWDIR/CTX/CTX000<VSID>/conf/local.arp)
The new line should look like this one below, where the MAC address should be the virtual MAC used by the security gateway on the incoming interface:
192.168.10.100 00:1C:7F:82:01:FE
After applying the policy, validate using:
fw ctl arp
The Equivalent of that using Gaia would be:
add arp proxy ipv4-address 192.168.10.100 interface eth0
And check with:
show arp proxy all