| In the Figure, traffic flows to the
router from the source VLAN, where it is routed to the destination
VLAN. This creates an out-and-back flow to the router. Technically,
the switch internal route switch module (RSM) uses a very similar
flow, but one important difference is the traffic uses the switch
backplane (the high-speed switching path used inside the switch
chassis). This difference provides two key benefits:
Because the RSM connects directly to
the backplane of the switch, it allows the router to be much more
tightly integrated with the switching process. Not only can this
ease configuration tasks, but it can provide intelligent
communication between the Layer 2 and Layer 3 portions of the
network. Also, because it provides a faster link than a single Fast
Ethernet ISL interface, performance is improved. In general, the RSM
provides 125,000-175,000 packets per second (pps) for IP and
approximately 100,000 pps for other protocols. If necessary, more
than one RSM can be used in a single switch chassis for additional
throughput.
|