Introduces default route concepts and their role in route management, helping users understand how default routes impact network forwarding decisions.
A default route is a routing configuration that
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directs packets destined for networks not explicitly listed in the routing table to a specified next hop,
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can be automatically or manually installed into a routing domain such as IS-IS, and
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is controlled and filtered using route policies to meet diverse network requirements.
Default route behavior in IS-IS routing domains
You can force a default route into an IS-IS routing domain. When you configure redistribution of routes into IS-IS, the software does not, by default, redistribute the default route. The default-information originate command generates a default route within IS-IS, which can be managed using route policies. Route policies allow you to identify the announcement level, specify other filtering options, and conditionally advertise the default route depending on the existence of another route in the router’s routing table.