Route Redistribution:
Route redistribution allows routes from one routing protocol to be advertised in another routing protocol.
Route redistribution is common in environments that support legacy equipment, proprietary protocols, or that have merged with other networks using a different routing protocol.
You must be careful when redistributing routes into another protocol because you may inadvertently create routing loops or suboptimal routes. Additionally, different routing protocols use different metrics, so you must take this into account when advertising one protocol into another.
Route Redistribution
It is fairly common to have multiple routing protocols running on the same router, since the routing protocols are independent; the routes learned are also independent. Route Redistribution allows routes learned via one routing protocol to be propagated by a different protocol.
Multi-protocol routing is common for a number of reasons, such as company mergers, multiple departments managed by multiple network administrators, and multi-vendor environments. Running different routing protocols is often part of a network design. In any case, having a multiple protocol environment makes redistribution a necessity.
Differences in routing protocol characteristics, such as metrics, administrative distance, classful and classless capabilities can effect redistribution. Consideration must be given to these differences for redistribution to succeed.