This document describes how the Cisco Email Security Appliance (ESA) supports Internet Protocol Version 6 (IPv6) address compatibility.
Individual or both IPv4 and IPv6 addresses can be assigned to the ESA IP Interface which is bound to the physical data ports on the device.
Note: IPv4 and IPv6 addresses with the same subnet cannot be configured on separate physical Ethernet interfaces. IPv6 addresses must use leading zeros, such as 2001:0db8:85a3:8a2e:0370:7334.
Listeners support both IPv4 and IPv6 addresses. You can use either protocol version or both on a single listener. The listener will use the same protocol version for mail delivery as the connecting host. For example, if the listener is configured for both IPv4 and IPV6 and connects to a host that uses IPv6, the listener uses IPv6. However if the listener is configured to only use IPv6 addresses, it cannot connect to a host that is only using IPv4 addresses.
Other Features Supporting IPv6 Address Entry
Gateways (default routers) and static routes, GUI: Network > Routing
SMTP Routes, GUI: Network >SMTP Routes
SMTP Call Ahead, GUI: Network >SMTP Call Ahead
Incoming Relays, GUI: Network >Incoming Relays
Trace, GUI: System Administration >Trace
Host Access Table (HAT) senders list within Sender Groups, GUI: Mail Policies >HAT Overview