The checkpoint knowledge base suggests you reboot to enable proxy arp. Not a great idea if you have a firewall cluster in production.

Check to see if proxy arp is enabled on your ethernet (eth0 in this example):

cat /proc/sys/net/ipv4/conf/eth0/proxy_arp

It will return 1 or 0, enabled or disabled.

To set:

echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp

Now you can use the arp command to publish a proxy arp entry, I like to use the hardware address of the ethernet we’re hiding behind ( -Ds parameter )

/sbin/arp -Ds (ipaddr you’re creating arp for) eth0 pub

/sbin/arp -Ds 10.20.30.100 eth0 pub