ZyXEL Communications ZyWALL 110 Handbook page 92

the User-Defined Original IP field and Type the translated destination IP address
that this NAT rule supports.
CONFIGURATION > Network > NAT > Add
Go to CONFIGURATION > Security Policy > Policy Control. IP forwarding must be
enabled at the firewall for the following IP protocols and UDP ports:
IP protocol = 50 → Used by data path (ESP)
IP protocol = 51 → Used by data path (AH)
UDP Port Number = 500 → Used by IKE (IPSec control path)
UDP Port Number = 4500 → Used by NAT-T (IPsec NAT traversal)
CONFIGURATION > Security Policy > Policy Control
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