In the OSPF (Open Shortest Path First) protocol, route redistribution refers to the process by which routes learned by one routing protocol are introduced into another.

In the specific case of OSPF, when routes from other routing protocols (such as RIP, EIGRP, or static routes) are redistributed within OSPF, they can be assigned as Type 1 (Type 1) or Type 2 (Type 2) routes.

This has to do with how the cost of these redistributed routes within the OSPF network is calculated.

Type 1 Routes (Type 1):

In this type of redistribution, the cost of the redistributed route is the sum of the original cost of the route in its source protocol plus the cost to reach the router that is performing the redistribution. In other words, the cost increases as the route passes through more OSPF routers, thus reflecting a cumulative metric that includes both the cost within OSPF and the cost of the route's original protocol.

Type 2 Routes (Type 2):

For Type 2 routes, only the external cost of the route as originally learned from the other protocol is considered, ignoring the cost to reach the router performing the redistribution.

The OSPF cost of reaching the redistribution point is not added to the cost of the redistributed route. This type of route keeps its external cost as the predominant value, regardless of how many OSPF hops the route must traverse.

The choice between Type 1 and Type 2 can affect route selection in the network, depending on the topology and the desired routing policy.

Type 1 may be more useful in networks where you want the metric to reflect the entire path through the OSPF network, while Type 2 may be preferred when the external cost must remain predominant over the internal OSPF costs.

This is crucial in environments where you want to control or manipulate route selection more precisely based on the original source of the route.