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Chapter 20: Unicast Routing
This switch can route unicast traffic to different subnetworks using the Routing
Information Protocol (RIP) or Open Shortest Path First (OSPF) protocol. It supports
RIP, RIP-2 or OSPFv2 dynamic routing. These protocols exchange routing
information, calculate routing tables, and can respond to changes in the status or
loading of the network.
RIP and RIP-2 Dynamic Routing Protocols
The RIP protocol is the most widely used routing protocol. RIP uses a
distance-vector-based approach to routing. Routes are determined on the basis of
minimizing the distance vector, or hop count, which serves as a rough estimate of
transmission cost. Each router broadcasts its advertisement every 30 seconds,
together with any updates to its routing table. This allows all routers on the network
to learn consistent tables of next hop links which lead to relevant subnets.
OSPFv2 Dynamic Routing Protocol
OSPF overcomes all the problems of RIP. It uses a link state routing protocol to
generate a shortest-path tree, then builds up its routing table based on this tree.
OSPF produces a more stable network because the participating routers act on
network changes predictably and simultaneously, converging on the best route more
quickly than RIP. Moreover, when several equal-cost routes to a destination exist,
traffic can be distributed equally among them.
Non-IP Protocol Routing
The switch supports IP routing only. Non-IP protocols such as IPX and Appletalk
cannot be routed by this switch, and will be confined within their local VLAN group
unless bridged by an external router.
To coexist with a network built on multilayer switches, the subnetworks for non-IP
protocols must follow the same logical boundary as that of the IP subnetworks. A
separate multi-protocol router can then be used to link the subnetworks by
connecting to one port from each available VLAN on the network.
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