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the high throughput and low latency of switching by enabling the traffic to bypass the
routing engine once the path calculation has been performed.
Routing Path Management
Routing Path Management involves the determination and updating of all the routing
information required for packet forwarding, including:
• Handling routing protocols
• Updating the routing table
• Updating the Layer 3 switching database
Routing Protocols
The switch supports both static and dynamic routing.
• Static routing requires routing information to be stored in the switch either manually
or when a connection is set up by an application outside the switch.
• Dynamic routing uses a routing protocol to exchange routing information, calculate
routing tables, and respond to changes in the status or loading of the network.
The switch supports RIP, RIP-2 and OSPFv2 dynamic routing protocols.
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.
3
IP Routing
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