Hello packet

As a CCNA / CCNP candidates is expected that you understand the purpose and function of OSPF protocol.

The CCNA / CCNP test consists of asking you to define the purpose of the OSPF hello packet, what it contains and what role it plays

Inside OSPF Hello Packet

OSPF routers build relationships with neighbors directly connected router hello by exchanging messages. OSPF routers exchange hellos, the ALLSPFROUTERS multicast destination address 224.0.0.5 up. OSPF sends Hello packet every 10 seconds with a hold time of 40secs on a broadcast link or point-to-point connection. OSPF sends Hello packet every 30 seconds with a hold time of 120secs in a non-broadcast link

Hey package includes the following information:

1. Router ID = Router ID, which is a 32-bit number that is unique to this router
2nd * Hello & DEAD INTERVALS = Hello and dead interval time between hellos and dead timers must match these values between two routers of the residents
3. NEXT LIST = is a list of the neighboring router, the router ID can see this as their neighbors
4th * Area = Area ID Area ID, this value must be between two routers is identical with neighbors
5th Retained ROUTER = router priority of this interface in the router's announcement of the highest priority are selected during the designated router DR / DBR electoral process.
6th The router ID = router ID, which considers that this router is the DR and BDR IP address of Designated Router
7th * AUTHENTICATION = If you set the authentication, it is important that the password between two routers for the residents.
8th * Stub area flag = on routers become neighbors is fixed in a stub, then stub area flag must

Two routers will first examine and exchange hi hi check the contents of the packages have the fields that match so do not match. If one of the areas not having routers can not be any kind of proximity neighbors, the cause of any expenses, execute the following command:

R1 # debug ip OSPF adj

If you see your neighbor proximity is formed as follows, where the state's full sentence is the adjacency matrix: R1 # show ip OSPF neighbors.

Neighbor ID Pri State Address Interface dead time

192.168.1.3 1 FULL / DR 00:00:39 192.168.1,3 Ethernet0 / 0

If you see your neighbor proximity as shown below, where the state 2-way neighbor relationship is formed, and that neighbor is neither the DR or BDR: R1 # show ip OSPF neighbors

Neighbor ID Pri State Address Interface dead time

192.168.1.3 1 2-WAY/DROTHER 00:00:39 192.168.1.3 Ethernet0 / 0

If you see your neighbor proximity as shown below, where the state is Exstart neighbors over, will determine the 2-way status and which device to facilitate the exchange of the summary of the link status database to start. If the state continues to show exstart may mean that the interface MTU size is not correct. Run "debug ip OSPF adj" command to a neighbor of the Education Committee.

R1 # show ip OSPF neighbors

Neighbor ID Pri State Address Interface dead time

192.168.1.3 1 Exstart / DR 00:00:39 192.168.1.3 Ethernet0 / 0