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Barracuda Web Security Gateway

When would virtual interfaces be needed without the use of VLANs?

  • Type: Knowledgebase
  • Date changed: 2 years ago

Solution #00006234


Barracuda Web Filter All Firmware Versions

The following scenario would require the use of vertical interfaces even if you are not using VLANs:
  1. The network is configured with multiple internal subnets.
  2. Thenetwork is configured to use the firewall to route between these internal subnets but does not have trunking or VLANs configured.
  3. Sub-interfaces are configured in each subnet on the firewall.
  4. There is no internal layer 3 switch on the network.
In this situation, you must obtain a free IP address in each subnet that is not the native subnet of the web filter. These IP addresses will be used to configure virtual interfaces to allow the web filter to reside in each subnet and be able to filter traffic for each subnet.


  1. In the Advanced Tab > Advanced Networking page under Virtual Interfaces, enter an IP address and corresponding subnet mask for your first additional subnet.
  2. The gateway address for this virtual interface should be set to the IP address on the firewall that is in the corresponding subnet.
  3. The device mode for the virtual interface should be set to bridge.
  4. Click the add button to add the virtual interface configuration.
  5. Repeat the steps for any additional subnets.
  6. Test ensure connectivity and proper filtering.

In this scenario, no configuration is required on Advanced > Advanced Network > IP Routing for these virtual interfaces to work correctly.