7. Steps to OSPF Operation with States
1. Establishing router adjacencies (Routers are adjacent)
–Down State – No Hello received
–Init State – Hello received, but not with this router’s Router ID
•“Hi, my name is Carlos.” “Hi, my name is Maria.”
–Two-way State – Hello received, and with this router’s Router ID
•“Hi, Maria, my name is Carlos.” “Hi, Carlos, my name is Maria.”
2. Electing DR and BDR – Multi-access (broadcast) segments
only
–ExStart State with DR and BDR
–Two-way State with all other routers
3. Discovering Routes (coming soon)
–ExStart State
–Exchange State
–Loading State
–Full State (Routers are “fully adjacent”)
4. Calculating the Routing Table
5. Maintaining the LSDB and Routing
Table
13. Step 3: Discover routes
–Down State – No Hello received
–Init State – Hello received, but not with this router’s Router ID
•“Hi, my name is Carlos.” “Hi, my name is Maria.”
–Two-way State – Hello received, and with this router’s Router ID
•“Hi, Maria, my name is Carlos.” “Hi, Carlos, my name is Maria.”
16. OSPF Configuration and
Verification
• Configuring OSPF on routers within a
single area
• Optional configuration commands
• Optional configuration commands
(continued)
• Show commands
• Clear and debug commands
17. Configuring OSPF on routers
within a single area
Rtr(config)# router ospf process-id
Rtr(config-router)#network address wildcard-mask area area-id
19. Optional configuration commands
(continued)
CISCO Routers use the formula = 108/bandwidth
Rtr(config-if)# bandwidth 64 = Rtr(config-if)# ip ospf cost 1562
Rtr(config-if)# bandwidth kilobits
Rtr(config-if)# ip ospf authentication-key passwd
Rtr(config-router)# area “area” authentication
Rtr(config-if)# ip ospf message-digest-key key-id md5 password
Rtr(config-router)# area area authentication [message-digest]
27. Multiarea OSPF Operation
• The routing table is too big, the memory is
running low
– Creating multiple OSPF areas
• OSPF router types
• OSPF LSA and area types
• Configuring OSPF operation across multiple
areas
• Flooding LSUs to multiple areas
• Updating the routing table
28. OSPF router types
• routers exchange LSAs via muticast;
• various types of LSA:
– Type 1 LSA router,
– Type 2 LSA network,
– Type 3 LSA network summary,
– Type 4 LSA ASBR next hope reachability,
– Type 5 LSA external LSA and
– Type7 LSA external NSSA route
35. Stub, Totally Stubby, and Not-So-
Stubby Areas
• Using stub and totally stubby areas
• Stub and totally stubby area criteria
• Configuring stub and totally stubby areas
• OSPF stub area configuration example
• OSPF totally stubby area configuration
example
• NSSA overview
• How NSSA operates
• Configuring NSSA