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A simpler method for
forcing a router to use a gateway of last resort for remote subnets
that are part of the local domain is to configure the
ip classless
command. This command causes the router to
ignore all aspects of address classes when making routing decisions.
The following excerpt from the router C configuration shows how
ip
classless
has been configured.
!
ip classless
!
Note:
The ip classless command is global. It affects all routing
protocols in the router. It should be used with caution. A thorough
discussion of all the implications of using this command is beyond
the scope of this book. Please refer to your Cisco IOS documentation
for more information.
In the
output of the show ip route command on router C, you can see
that, once again, router C has no knowledge of how it should route
packets for 168.71.6.0. (see RouterC#show ip
route 168.71.6.0 command
output).
In the
output from router C pinging 168.71.6.1, you can see that the ping
is successful. (see RouterC#ping
168.71.6.1 command
output).
As you can see,
router C can ping a local domain subnet that it has no knowledge of,
even though the local domain default route pointing to 10.0.0.0 (ip
route 168.71.0.0 255.255.0.0 10.0.0.0) has not been configured.
Remember that this was a required configuration parameter before the
ip classless command was configured.
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