4.CCNA, CCNP configuration OSPF study notes summary
Lesson 15 OSPF
First, OSPF Introduction 1. Open ShortestPath Fir. St 2. It is a dynamic routing protocol, the international standard,reference material is RFC2328. 3. LinkS‐tate, a protocol based on link state. 4. Fast convergence, lowbandwidth consumption, support for VLSM & CIDR. 5. Three versions: Version1 is in the lab; Version 2 is for IPv4 services; Version 3 is for IPv6services.
6. Link ‐ S: ta chain te state; knowledge of the network comes from theoriginating router, with global topology, reliable transmission (flooding) LSAbetween neighbors. 7. Distance ‐Vec: todistance from r vector; knowledge of the network comes from direct neighbors.Simple but inevitable cycle. 8. Divide the area ‐‐minus-light agreement pressure: Unnecessarily flooding the LSAthrough the area.
Second, the working mechanism of OSPF
1. Protocol packet type: HELLO: used toestablish and maintain neighbor relationship, DBD: used to verify the databasebetween routers and synchronize, LSR: link state request, request specific LSAto the neighbor, LSU: link status update, Carry the LSA to advertise the routeto the neighbor, LSAck: Confirm, confirm the received LSA
2. Encapsulation: Directly encapsulated byIP, IP protocol number 89, source IP using egress IP, target
IP : 220.127.116.11 ( ALL OSPF ROUTE) R, S18.104.22.168 (ALL OSPF DR & BDR ROUTER) S
3. Workflow: three phases: exchange phase;route discovery phase; routing