Why BVI is Required in the Transparent Cisco IOS Firewall

C.

In the Transparent Cisco IOS Firewall, a Bridge Virtual Interface (BVI) is required to provide connectivity between the firewall interfaces and the bridging engine. The purpose of the BVI is to allow the firewall to inspect traffic that passes through the bridge, which means that answer A, "BVI is required for the inspection of IP traffic," is correct.

When traffic flows through the firewall, it passes through a virtual bridge group that is created by the firewall. This bridge group can consist of one or more interfaces, which are connected to the firewall. The BVI provides the IP address for the virtual bridge group and enables the firewall to perform Layer 2 and Layer 3 inspection on the traffic that passes through it.

Answer B, "BVI is required if routing is disabled on the firewall," is incorrect because routing is not related to the use of BVI in the Transparent Cisco IOS Firewall. However, routing is not supported in the Transparent Firewall mode, which is different from disabling routing.

Answer C, "BVI is required if more than two interfaces are in the same bridge group," is incorrect because the number of interfaces in a bridge group is not related to the use of BVI.

Answer D, "BVI is required for the inspection of non-IP traffic," is incorrect because the BVI is used for inspecting IP traffic only. The Cisco IOS Firewall does not support non-IP traffic inspection.

Finally, answer E, "BVI cannot be used to manage the device," is also incorrect because the BVI can be used to manage the firewall device. In fact, the BVI is often used as the management interface for the firewall because it is the only interface that has an IP address assigned to it.

In conclusion, the correct answer is A, "BVI is required for the inspection of IP traffic," because the BVI provides connectivity between the firewall interfaces and the bridging engine, allowing the firewall to inspect traffic that passes through the bridge.