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Chapter 6
Troubleshooting TCP/IP Connectivity
are important in router initialization and for DR and BDR selection. You can
change these values with some minor configuration changes.
To change the router priority, use the following command on the desired
interface:
ip ospf priority number
The number can range from 0 to 255--the higher value indicates a higher
priority when choosing the DR and BDR for the area.
Just as with EIGRP, new metrics must be assigned to route information
that is injected into the OSPF session. The command is much simpler than
the command used when assigning metrics for EIGRP or IGRP--it is almost
the same, but only one metric is assigned. The value of the metric is the cost
for the route.
default-metric cost
Distribute Lists
Distribute lists are access lists applied to an interface from within a routing
protocol. The purpose of a distribute list is to control which routes are adver-
tised to adjacent routers.
Problems can occur if distribute lists are missing or improperly config-
ured. Figure 6.13 shows a picture of three meshed routers. Undesired routing
can occur if the advertised routes are not controlled through the use of dis-
tribute lists.
F I G U R E 6 . 1 3
Distribute lists to prevent routing loops
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