Distance Vector Routing is a type of routing algorithm used in network layer for determining the best path for data transmission. It is also known as Bellman-Ford algorithm or Distributed Bellman-Ford algorithm.
In Distance Vector Routing, each router maintains its own routing table and shares information about its own distance to other routers in the network. Each router periodically sends its entire routing table to its neighboring routers. The distance vector used in this algorithm is the number of hops or the cost to reach the destination network. The routers keep track of the distance to all possible destinations in the network and the next hop to reach the destination.
The routing table of each router is updated based on the received information from its neighbors. If a router receives an update with a better path to a destination network, it updates its own routing table.
Distance Vector Routing is easy to implement and requires less computational power than other routing algorithms. However, it suffers from slow convergence and routing loops.
Example:
Step 1:
Each router shares its routing table with every neighbor in this distance vector routing network. As A will share its routing table with neighbors B and C, neighbors B and C will share their routing table with A.
Routing table A:
| FORM A | A | B | C |
|---|---|---|---|
| A | 0 | 1 | 5 |
| B | |||
| C |
Routing table B:
| FORM A | A | B | C |
|---|---|---|---|
| A | |||
| B | 1 | 0 | 2 |
| C |
Routing table C:
| FORM A | A | B | C |
|---|---|---|---|
| A | |||
| B | |||
| C | 5 | 2 | 0 |
Step 2:
If the path via a neighbor has a lower cost, the router updates its local table to forward packets to the neighbor. In this table, router A will be updated.
Routing table A:
| FORM A | A | B | C |
|---|---|---|---|
| A | 0 | 1 | 3 |
| B | |||
| C |
Routing table B:
| FORM A | A | B | C |
|---|---|---|---|
| A | |||
| B | 1 | 0 | 2 |
| C |
Routing table C:
| FORM A | A | B | C |
|---|---|---|---|
| A | |||
| B | |||
| C | 3 | 2 | 0 |
Step 3:
The following are the final routing table for all the routers A, B, and C with lower cost distance vector routing protocols.
Router for table A:
| FORM A | A | B | C |
|---|---|---|---|
| A | 0 | 1 | 3 |
| B | 1 | 0 | 2 |
| C | 3 | 2 | 0 |
Router for table B:
| FORM A | A | B | C |
|---|---|---|---|
| A | 0 | 1 | 3 |
| B | 1 | 0 | 2 |
| C | 3 | 2 | 0 |
Router for table C:
| FORM A | A | B | C |
|---|---|---|---|
| A | 0 | 1 | 3 |
| B | 1 | 0 | 2 |
| C | 3 | 2 | 0 |