Avaya 580 - Manual (Page 47)

Document No. 10-300077, Issue 2 1-23
Introduction
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Since layer 2 modules have no routing capability, packets that are
received by a layer 2 module and require routing are forwarded by
sending the packet to the 50-series layer 3 or 80-series supervisor
module. The routing engine on the supervisor module then performs
the routing operation for the layer 2 modules and sends the packet
back through the switching fabric to the destination port.This is
referred to as the FORE path, or Fast Out of Bands Routing Engine,
since the routing is accomplished in the hardware of either
supervisor module.
Figure 1-3 shows how traffic is routed in a switch.
Figure 1-3. Layer 2 and Layer 3 Routing in a Switch