Transit Traffic

B

Transit traffic refers to network traffic that passes through a networking device, such as a router or switch, without being targeted for the device itself. Transit traffic can be either Layer 2 or Layer 3 traffic, and it is typically routed through the device based on its destination IP address.

Option A in the question states that transit traffic is traffic addressed to the chassis that requires special handling by the Routing Engine (RE) before it can be forwarded out an egress port. This is not correct. The RE typically handles control plane functions such as managing routing protocols, but transit traffic is not addressed to the chassis itself.

Option B states that transit traffic enters an ingress port, is compared against the forwarding table, and is forwarded out an egress port. This is the correct definition of transit traffic. When a networking device receives traffic on an ingress port, it examines the destination IP address of the traffic and looks it up in its forwarding table. If the device finds a matching entry in its forwarding table, it forwards the traffic out the corresponding egress port. If the traffic is not targeted for the device itself, it is considered transit traffic.

Option C states that transit traffic is any traffic that requires the generation of an ICMP message. This is not correct. ICMP messages are used for network troubleshooting and error reporting, and they are not related to transit traffic specifically.

Option D states that transit traffic requires special attention and does not pass through the device. This is not correct. Transit traffic does pass through the device, but it is not targeted for the device itself. It is simply passing through on its way to its destination.

In summary, the correct answer is Option B, which correctly describes transit traffic as traffic that enters an ingress port, is compared against the forwarding table, and is forwarded out an egress port.