OSPF Hello Packets

Open Shortest Path First Hello Packets are the packets that when you configure the OSPF routing protocol on the routers your routers will start sending the packets to each other for the establishment of the neighbor ship and if you also receive the hello packets from the other router you will become neighbors. And once we have become the neighbors we going to exchange link state advertisements. OSPF hello packets are the firsts packets that are received and transmit for the Open shortest path first processing so these are the packets that are used for the maintain and establishing of the neighbors. These packets are the packets that are encapsulate in the IP and the protocol number that is in the IP header is 89 that are sent to the OSPF router on the basis of the multicast address that is 224.0.0.5 .

OSPF Hello Packets Contain the following terms that are very important things for the establishment of the neighbor ship of the OSPF routers:

Fig 1 : OSPF Hello Packet

1. Router ID(It is the identification of the router in the OSPF and it is the highest IP address).
2. Hello/Dead Interval (If we don't receive any update for x seconds then we declare "dead". 
3. Neighbors
4. Area ID(This is the area you are in).
5. Router Priority(This specify the who will become the DR and BDR).
6. DR IP Address(Designated Router's IP Address).
7. BDR IP Address(Backup Designated Router's IP Address).
8. Authentication(md5 is the authentication of  OSPF if both routers have same passwords).
9. Password
10. Stub Area Flag(Is is for the defining of which router's interface is stub) in the ospf it is just a bit that is known as the E bit and it value can be 1 or 0.