How does the PFE handle unicast transit traffic destined for an existing forwarding table entry?

A

In Junos, PFE (Packet Forwarding Engine) is responsible for forwarding transit traffic, and it operates independently of the Routing Engine (RE). The PFE processes packets based on the forwarding table entries that are programmed into it by the RE.

When the PFE receives unicast transit traffic that is destined for an existing forwarding table entry, it examines the entry's forwarding information to determine the egress interface or interfaces for the packet. The PFE then forwards the packet through the appropriate egress interface or interfaces toward its destination.

So, the correct answer to this question is A: It sends the traffic through one egress port toward its destination.

Option B is not correct because the PFE does not send traffic through multiple egress ports to all available receivers. It only forwards the traffic through the egress port or ports specified in the forwarding table entry.

Option C is also not correct because the PFE does not send transit traffic through an internal link to the RE. The RE is responsible for programming the PFE's forwarding table entries but does not handle transit traffic forwarding.

Option D is not correct because the PFE does not send transit traffic to the local system for further processing. The PFE handles transit traffic forwarding independently of the RE.

In summary, when the PFE receives unicast transit traffic destined for an existing forwarding table entry, it forwards the traffic through one egress port toward its destination.