Network Warrior

Redistributing into OSPF

Redistribution into OSPF is done in the same way as in the other protocols. The metric for an OSPF route is a derivative of the bandwidths of the links contained in the route. Setting the default metric in OSPF to 10 Mbps is done as follows:

R3(config-router)#default-metric 10

There are no other options. The metric can have a value of 1–16,777,214, with 1 being 100 Mbps (assuming default settings).

Tip

If you do not specify a default metric or a metric on the redistribute command line, OSPF will assign a metric of 20 to all redistributed routes, except those from BGP, which will be assigned a metric of 1.

While all redistributed routes are external, OSPF supports two types of external routes, which are cleverly described as type-1 and type-2 external routes. Type-1 routes are designated with O E1 in the routing table, while type-2 routes are designated with O E2. E1 routes include the metric as set at the point of redistribution, plus the metric of all the links within the OSPF autonomous system. E2 routes only include the metric set at the point of redistribution. Figure 11-4 illustrates how the OSPF metrics change throughout a simple network depending on the external route type in use.

Figure 11-4. OSPF external route types

Redistribution into OSPF defaults to type-2 routes. Which type should you use? That depends on your needs at the time. Generally, in smaller ...