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The Network Address Translation (NAT) gateway provides translation services between external and internal IP addresses and utilizes a separate network connection on each of the two MMCS.
On PowerMax, there are two Network Address Translation (NAT_ IP addresses for eNAS, one per each NAT gateway. Both the IP addresses are mapped to different interfaces on the CS and source routed accordingly. So, for any incoming connections, the CS can be reached using either of the IP addresses unless there is a failure with any of the NAT gateways on the PowerMax.
There is also a default route (using NAT1 initially) that is used for any communication originating on the CS. In case of a failure of default gateway, the route is changed to use the other NAT gateway. There is a monitoring daemon that checks the health of the NAT gateways and updates the switch with the route as necessary.
The above works as is for IPv4. Hence, it is active/active for IPv4. For IPv6, there is no capability to use both the gateways at the same time. So, it is active/passive. For IPv6, CS can be reached only through one NAT IP address (NAT1 initially), and when there is a failure there, it can be reached using the other NAT.