If an intermediate node receives another RREP after propagating the first RREP towards source it checks for destination sequence number of new RREP. The intermediate node updates routing information and propagates new RREP only,
• If the Destination sequence number is greater, OR
• If the new sequence number is same and hop count is small, OR
Otherwise, it just skips the new RREP. This ensures that algorithm is loop-free and only the most effective route is used.
The below Fig.1.3 is an example, which shows how the route to the destination is found by AODV routing protocol.
1. Source ’S’ has to send data to destination.
2. S sends RREQ to its neighbours A, B, C.
3. B finds the path in its routing table (with destn seq-number s1 and hop count c1) and sends RREP to S.
4.
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C sets up reverse path.
5. C forwards RREQ to its neighbours D and E.
6. E sets up reverse path.
7. E forwards RREQ to its neighbours F and G.
8. E deletes the reverse path after a time out period as it does not receive any RREPs from F and G.
9. D finds the path (with dest seq-number s2 which is greater than s1 and hop count c1) in its routing table and sends RREP to C.
10. C receives RREP from D and sets up forward path and forwards RREP to