Open Shortest Path First (OSPF)

Correct Answer: Use the 'default-information originate' command

In OSPF routing protocol, the 'default-information originate' command is used to generate a default external route into the OSPF domain. This command announces a 0.0.0.0/0 route and makes the router a default gateway. It is known to be the most efficient way to get OSPF to advertise a default route. Using a static default route or redistributing static routes would not necessarily resolve the problem of missing OSPF default routes, they can be used to provide a default route, but they are not the recommended approach in the context of OSPF. Increasing OSPF cost does not help to advertise default routes, it actually changes the path metric which might in turn influence the route selection process, but it would not help with the problem of missing default routes.

Correct Answer: Misconfigured network statement

The best possible answer is 'Misconfigured network statement'. In OSPF routing protocol, network statements are crucial as they confirm which interfaces participate in OSPF and in which areas. If a network statement is set up erroneously, it could prevent a route from being propagated. The 'Incorrect OSPF area' could also be looked at, but it is less likely to be the direct cause of a single missing route, and would more commonly affect a larger amount of routes. Both 'Mismatched OSPF timers' and 'Incorrect authentication' would typically cause none of the OSPF routes to be advertised, making them unlikely causes of only one route being missing.

Correct Answer: Configure OSPF summarization

The best solution to the problem of OSPF generating excessive updates is to 'Configure OSPF summarization'. This allows the bundling of multiple routes into a single summary route, thereby reducing the number of routing updates. On the other hand, 'Configure OSPF multi-area', 'Redistribute the routes', and 'Alter the hello timers' do not directly reduce the number of routing updates. 'Configuring OSPF multi-area' splits the network into different areas but does not limit routing updates in itself. 'Redistributing the routes' can lead to complex routing situations and uncontrolled routing updates if not properly managed. 'Altering the hello timers' adjusts the frequency of OSPF hello packets, but this does not directly relate to the volume of routing updates.