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Copyright © 1997 Cisco Systems, Inc.
6-33CSE: Networking Fundamentals — WAN Basics
© 1999, Cisco Systems, Inc.
www.cisco.com
Routing Decisions
Routing Decisions
– Routing protocols maintain a loop-free, single
path to each destination network
– Routes are advertised with a reachability
factor referred as a metric
– The path to the destination network is
represented by the sum of the metrics
associated with all intermediate links
– The routing process uses the metric value to
select a preferred path to each destination
• Multiple paths can be used if metric values
are equal
6-34CSE: Networking Fundamentals — WAN Basics
© 1999, Cisco Systems, Inc.
www.cisco.com
RIP Routing Metrics
RIP Routing Metrics
– Routing metric used by RIP is hop count
• Using a neighboring router interface is a hop
– Routing process arbitrarily selects a path from
several possible equal metric paths
• IP load balancing is enabled by default
TR
10.0
5.1
5.2
5.3
5.4
C 4.0 dir conn Ser0
C 5.0 dir conn Eth0
R 10.0 [120/4] via 5.2, Eth0
R 10.0 [120/4] via 5.3, Eth0
R 10.0 [120/4] via 5.4, Eth0
4.0
FDDI
These Addresses Are All Part
of the 192.168.0.0 Network
These Addresses Are All Part
of the 192.168.0.0 Network
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