|  | 11.3 | Distance-Vector Routing
| 11.3.1 | Distance-vector routing basics
Distance-vector-based routing algorithms pass periodic copies of a routing table from router to router. These regular updates between routers communicate topology changes. Each router receives a routing table from its directly neighboring routers. For example, in the graphic, Router B receives information from Router A. Router B adds a distance-vector number (such as a number of hops), which increases the distance vector and then passes this new routing table to its other neighbor, Router C. This same step-by-step process occurs in all directions between direct-neighbor routers. The algorithm eventually accumulates network distances so that it can maintain a database of network topology information. Distance-vector algorithms do not, however, allow a router to know the exact topology of an internetwork.