The state of the conversation between the OSPF peers trying to build an adjacency. OSPF neighbors go through various stages of conversation & each OSPF state defines that stage & the actions performed at that stage. OSPF states are maintained on per interface basis and doesn’t represent the complete OSPF Process.
There are 8 OSPF neighbor states in total. They are:
1. Down – Our router is sending OSPF hellos, but No OSPF hello messages have been received from the neighbor.
2. Attempt – Only seen, when manual neighbors are defined in NBMA networks. It means that our router is sending unicast hello messages, but hasn’t received any reply yet.
3. Init – It simply means that the router did received hello messages from a neighbor, but they don’t have the Router ID of the receiving router, as a known neighbor.
4. 2-Way – It means that router did receive hello message from neighbor & that hello message includes its Router ID. This means the both routers are able to see each other Hello Messages, which also means that now they have 2-way communication going on. If required, The DR and BDR will be elected at the end of this stage, before moving on to next OSPF neighbor state.
5. Ex-Start – The actual process of LSA/LSDB information exchange begins with this stage. This is where the master/slave relationship is established and the initial sequence numbers are exchanged.
6. Exchange – In this OSPF neighbor state, DBD packets are exchanged. These packets only contain the LSA header information. This information will be used by routers to see what LSA’s they have and what LSA’s they don’t have.
7. Loading – This is where the actual exchange of OSPF Database information happens. On basis of the information gathered in the above stage, Link State Requests (LSR’s) are generated to request for missing LSA’s and the requests are fulfilled by Link State Update (LSU’s) packets.
8. Full - Once both routers have a synchronized database after the LSR/LSU exchange process, they exchange LSAck’s with each other in order to confirm & then move on to Full state.
There are 8 OSPF neighbor states in total. They are:
1. Down – Our router is sending OSPF hellos, but No OSPF hello messages have been received from the neighbor.
2. Attempt – Only seen, when manual neighbors are defined in NBMA networks. It means that our router is sending unicast hello messages, but hasn’t received any reply yet.
3. Init – It simply means that the router did received hello messages from a neighbor, but they don’t have the Router ID of the receiving router, as a known neighbor.
4. 2-Way – It means that router did receive hello message from neighbor & that hello message includes its Router ID. This means the both routers are able to see each other Hello Messages, which also means that now they have 2-way communication going on. If required, The DR and BDR will be elected at the end of this stage, before moving on to next OSPF neighbor state.
5. Ex-Start – The actual process of LSA/LSDB information exchange begins with this stage. This is where the master/slave relationship is established and the initial sequence numbers are exchanged.
6. Exchange – In this OSPF neighbor state, DBD packets are exchanged. These packets only contain the LSA header information. This information will be used by routers to see what LSA’s they have and what LSA’s they don’t have.
7. Loading – This is where the actual exchange of OSPF Database information happens. On basis of the information gathered in the above stage, Link State Requests (LSR’s) are generated to request for missing LSA’s and the requests are fulfilled by Link State Update (LSU’s) packets.
8. Full - Once both routers have a synchronized database after the LSR/LSU exchange process, they exchange LSAck’s with each other in order to confirm & then move on to Full state.
No comments:
Post a Comment