If your organization has a single public IP address, when you install the Barracuda Email Security Gateway between the Internet and your mail server, you can forward incoming SMTP traffic (port 25) from port 80 on the Barracuda to your mail server using the Port Forwarding feature from the ADVANCED > Advanced Networking page.
Configuring the Network Interfaces
With the Barracuda Email Security Gateway 600 and higher, you can configure each of the two Ethernet (NICS) interfaces directly from the ADVANCED > Advanced Networking page to accept email on both interfaces or to route ingress email to one NIC and egress through the other NIC. Benefits of this feature include redundancy, filtering email for domains on separate networks and improving throughput. Up to 250 IP addresses can be configured per NIC.
With the Barracuda Email Security Gateway 600 (and 600Vx) and higher, you can specify a default gateway between the Barracuda Email Security Gateway and a mail server on another subnet in your organization using the Static Routes feature on the ADVANCED > Advanced Networking page. This will guarantee that return traffic is routed back to the Barracuda Email Security Gateway from the unassociated network. If you have problems with static route configuration, please contact Barracuda Networks Technical Support.
If you want to use this Barracuda Email Security Gateway with a Barracuda Load Balancer in Direct Server Return mode, you must enable a non-ARPing loopback adapter. If you are using any other mode you do not need to make any changes to the Barracuda Email Security Gateway configuration.
Each Virtual IP address supported by the Real Server (the Barracuda Email Security Gateway in this case) requires its own loopback adapter. For each loopback adapter, enter a Virtual IP address in the Loopback Adapter Configuration field on the ADVANCED > Advanced Networking page.