Understanding the FEB

Purpose

Inspect the FEB to ensure that communication occurs with the Routing Engine.

What Is an FEB

The FEB is a control board for the M5 and M10 routers (see Figure 180). The FEB communicates with the Routing Engine using a dedicated 100-Mbps link that transfers routing table data from the Routing Engine to the forwarding table in the Internet Processor II application-specific integrated circuit (ASIC). The link is also used to transfer routing link-state updates and other packets destined for the router from the FEB to the Routing Engine. The FEB provides the following functions:

• Route lookups—The Internet Processor II ASIC on the FEB performs route lookups using the forwarding table stored in synchronous SRAM (SSRAM).
• Shared memory management—One Distributed Buffer Manager ASIC on the FEB uniformly allocates incoming data packets throughout the router's shared memory.
• Outgoing data packet transfer—A second Distributed Buffer Manager ASIC on the FEB passes data packets to the destination Physical Interface Card (PIC) when the data is ready to be transmitted.
• Exception and control packet transfer—The Internet Processor II ASIC passes exception packets to the microprocessor on the FEB, which processes almost all of them. The remaining packets are sent to the Routing Engine for further processing. Any errors originating in the Packet Forwarding Engine and detected by the FEB are sent to the Routing Engine using system log messages.

Figure 180: FEB Component

The FEB is located on the rear of the router above the power supplies (see Figure 181).

Figure 181: M5 and M10 Router FEB Location

The FEB is field-replaceable, but is not hot-removable or hot-pluggable. You must power down the router before removing or replacing the FEB.