admin- Posted on
The OSPF Hello
As a CCNA / CCNP candidate you’re anticipated to know the aim and performance of the OSPF protocol.
The CCNA / CCNP’s examination will ask of you to find out the aim of the OSPF howdy packet, what it accommodates and the position it performs
Contained in the OSPF Good day Packet
OSPF routers create neighbor relationships with instantly related routers by exchanging howdy messages. OSPF Router trade hellos addressed to the ALLSPFROUTERS multicast vacation spot tackle of 224.0.0.5. OSPF sends out howdy packets each 10 seconds with a maintain time of 40secs on a broadcast hyperlink or Level-to-point hyperlink. OSPF sends out howdy packets each 30 seconds with a maintain time of 120secs on a non-broadcast hyperlink
The Good day Packet accommodates the next knowledge:
1. ROUTER ID = Router ID, it is a 32-bit quantity that’s distinctive to this router
2. *HELLOS & DEAD INTERVALS = Good day and useless interval Time frame between hellos and the useless timer, these values should match between two routers changing into neighbors
3. NEIGHBOUR LIST = Is a Record of neighbor Router Ids that this router sees as their neighbor
4. *AREA ID = Space ID Space quantity, this worth have to be similar between two routers changing into neighbors
5. ROUTER PRIORIY = Router Precedence of this interface, the router promoting the very best precedence is elected the designated router through the DR/DBR election course of.
6. ROUTER ID = The Router ID of who this router believes is the DR and BDR IP tackle of designated routers 7. *AUTHENTICATION = You probably have authentication set it’s important that the Password matches between the 2 routers changing into neighbors.
8. *STUB AREA FLAG = If the routers changing into neighbors are in a Stub Space, then the Stub Space Flag have to be set
Two routers will initially trade howdy and study the contents of the Good day Packets to confirm that the fields which must match do certainly match. If any of the fields don’t match the routers can’t kind any neighbor adjacency, to view the explanations for any doable points run the next command:
R1#debug ip ospf adj
When you see your neighbour adjacency like beneath, the place the state is FULL means the adjacency has fashioned: R1#present ip ospf neighbor.
Neighbor ID Pri State Lifeless Time Handle Interface
192.168.1.3 1 FULL/DR 00:00:39 192.168.1.3 Ethernet0/0
When you see your neighbour adjacency like beneath, the place the state is 2-way means the neighbour relationship has fashioned and that the neighbour is neither the DR nor the BDR: R1#present ip ospf neighbor
Neighbor ID Pri State Lifeless Time Handle Interface
192.168.1.3 1 2-WAY/DROTHER 00:00:39 192.168.1.3 Ethernet0/0
When you see your neighbour adjacency like beneath, the place the state is Exstart the neighbors are previous the 2-way state and are figuring out which machine goes to start out the trade of the abstract of the Hyperlink state database. If the state continues to show exstart can imply that the Interface MTU sizes are mismatched. Run the “debug ip ospf adj” command to point out any neighbour formation points.
R1#present ip ospf neighbor
Neighbor ID Pri State Lifeless Time Handle Interface
192.168.1.3 1 Exstart/DR 00:00:39 192.168.1.3 Ethernet0/0