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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration Guide
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Chapter32 Configuring IP Unicast Routing Configuring Protocol-Independent Features
When default information is passed through a dynamic routing protocol, no further configuration is
required. The system periodically scans its routing table to choose the optimal default network as its
default route. In IGRP networks, there might be several candidate networks for the syste m default. Cisco
routers use administrative distance and metric information to set the default route or the gatew ay of last
resort.
If dynamic default information is not being passed to the system, candidates for the default route are
specified with the ip default-network global configuration command. If this network appears in the
routing table from any source, it is flagged as a possible choic e for the default route. If the router has no
interface on the default network, but does have a path to it, the network is considered as a possible
candidate, and the gateway to the best default path becomes the gateway of last resort.
Using Route Maps to Redistribute Routing Information
The switch can run multiple routing protocols simultaneously, and it can redistribute information from
one routing protocol to another. Redistributing information from one routing protocol to another applies
to all supported IP-based routing protocols.
You can also conditionally control the redistribution of routes between routing domains by defining
enhanced packet filters or route maps between the two domain s. The match and set rout e-ma p
configuration commands define the condition portion of a route map. The match command spec ifies that
a criterion must be matched; the set command specifies an action to be taken if the routing update meets
the conditions defined by the match command. Although redistribution is a p rotocol -in dep ende nt
feature, some of the match and set route-map configuration commands are specific to a particular
protocol.
One or more match commands and one or more set commands follow a route-map command. If there
are no match commands, everything matches. If there are no set command s, nothing is done, other than
the match. Therefore, you need at least one match or set command.
You can also identify route-map statements as permit or deny. If the statement is marked as a deny, the
packets meeting the match criteria are sent back through the normal forwarding channe ls
(destination-based routing). If the statement is marked as permit, set clauses are applied to packets
meeting the match criteria. Packets that do not meet the match criteria are forwarded through the normal
routing channel.
Note Although each of Steps 3 through 14 in the following section is o pti onal , you m ust e nte r at leas t on e
match route-map configuration command and one set route-map configuration command.