Cisco Cisco Email Security Appliance C160 Mode D'Emploi

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Cisco AsyncOS 8.5.6 for Email User Guide

Chapter 36 Advanced Network Configuration

Direct Server Return

Figure 36-3

Using a VLAN when Creating a New IP Interface via the GUI

Direct Server Return

Direct Server Return (DSR) is a way of providing support for a light-weight load balancing mechanism
to load balance between multiple Email Security appliances sharing the same Virtual IP (VIP).

DSR is implemented via an IP interface created on the “loopback” ethernet interface on the appliance.

Note

Configuring load balancing for Email Security appliances is beyond the scope of this document.

Enabling Direct Server Return

Enable DSR by enabling the “loopback” ethernet interface on each participating appliance. Next, create
an IP interface on the loopback interface with a virtual IP (VIP) via the

interfaceconfig

command in

the CLI or via the Network -> Interfaces page in the GUI. Finally, create a listener on the new IP interface
via the

listenerconfig

command in the CLI or via the Network -> Listeners page in the GUI.

Remember to commit all changes.

Note

Using the loopback interface prevents the appliance from issuing ARP replies for that specific interface.

When enabling DSR, the following rules apply:

–

All systems use the same Virtual IP (VIP) address

–

All systems must be on the same switch and subnet as the load balancer