What command would you use to summarize routes in OSPF?

The command to summarize routes in OSPF is "summary-address." This command is used within an OSPF router configuration to create a summarized route for multiple underlying routes, enhancing routing efficiency and reducing the size of the routing table. When using this command, you specify the address and prefix length of the summarized route.

For instance, if there are several OSPF routes in a network that can be summarized into a single entry, using the "summary-address" command helps streamline the routing process by allowing routers to handle fewer routes, which leads to faster convergence and reduced overhead. This is particularly useful in larger networks where route aggregation can significantly reduce the complexity of routing tables.

Other options do not correctly accomplish route summarization in OSPF. For example, "distribute-list summary" refers to filtering routes based on a distribute list rather than summarizing them. "ip route summarize" is not a valid command in OSPF or Cisco IOS. Lastly, "default-route" is used to define a route that should be used when no specific routes are available, and it does not perform summarization of existing routes.