Kevin Piper, David Perry, Tom Hoffman, Emely Pagan OSPF Kevin Piper, David Perry, Tom Hoffman, Emely Pagan 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Agenda OSPF overview Configuring single area OSPF lab Router designation Configuring multi-area OSPF lab Verifying and managing OSPF Questions or comments 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Overview OSPF (open shortest path first). A link state protocol. Link state protocols use the shortest path first algorithm to populate the routing table. OSPF shares information with every router on the network. OSPF and Cisco. OSPF is nonproprietary to Cisco. Developed 1988 by internet engineering task force (IETF). Developed to be a interior gateway protocol. Used by routers in the same autonomous system. 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College OSPF Terms Designated Router (DR) Backup DR Priority Autonomous System (AS) Area Border Router (ABR) Link State advertisement (LSA) Router ID Topology Table Adjacency Link state Area Cost 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Configuring Cost Cost 64.7 Cost 64.7 1.544MB R4 1.544MB R3 R5 Cost 1 Cost =1562 Cost =195.1 100MB 56KB Cost 1562 R1 1.544MB R2 Cost 64.7 Cost = 10^8 / bandwidth 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Pros and Cons Advantages Supports VLSM Faster convergence Efficient bandwidth utilization No hop-count limit Path selection based on cost Loop-free routing environment Disadvantages Difficult to configure More time to plan CPU/memory intensive 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Considerations Size of the area Number of neighbors per router Problem isolation Restriction of routing information Stable backbone design Addressing areas 6/1/2018 Valencia Community College Cisco Networking

OSPF packet header Hello Packet 6/1/2018 Valencia Community College Authentication Length Description 8bytes Packet Length Type 4 bytes 1 byte Version Number 2 bytes Authentication type Check sum Area ID Router ID Hello Packet Additional Neighbor Length Description 4 bytes each Hello interval Netmask 1 byte 24 bytes OSPF Packet Header 2 bytes 4 bytes Designated router Backup designated router Dead interval Router Priority option 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Forming Adjacencies Init state Establish bi-directional communication Exstart Exchange state Loading state Full state 6/1/2018 Valencia Community College Cisco Networking

Router Adjacencies Without Designated Routers 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Router Designation Election process Hello Packet Priority Designated router (DR) Backup DR (BDR) DR other 6/1/2018 Valencia Community College Cisco Networking

Router Adjacencies With Designated Routers BDR 9 Router adjacencies R4 DR 6/1/2018 Valencia Community College Cisco Networking

Configuring Single Area OSPF 6/1/2018 Valencia Community College Cisco Networking

Single Area OSPF Layout 131.108.1.2/24 131.108.1.1/24 R3’s Loopback R3’s Loopback Router 1 E0 Loopback0 11.11.11.11 E0 Loopback0 22.22.22.22 Switch Router 2 E0 131.108.1.3/24 Router 3 R3’s Loopback Loopback0 33.33.33.33 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Configuration Files Router 1 Router 2 Router 3 6/1/2018 Valencia Community College Cisco Networking

Configuring Multi-area OSPF Why use multi-area OSPF ? Advantages Smaller routing tables Less routing update overhead Faster synchronization Disadvantages Complex to implement 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College OSPF Router Types Internal Area border router (ABR) Autonomous systems border router (ASBR) Backbone router 6/1/2018 Valencia Community College Cisco Networking

Multi-area OSPF Layout Switch 131.108.1.2/24 131.108.1.1/24 Area 1 E0 Router 1 E0 Router 2 S0 Area 2 141.108.10.0/30 S1 141.108.10.4/38 Router 3 S1 S0 E0 E0 131.108.26.1/24 131.108.33.1/24 Router 4 Area 0 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Router 1 configuration 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Router 2 configuration 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Router 3 Configuration 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Router 4 configuration 6/1/2018 Valencia Community College Cisco Networking

Verifying and Managing OSPF OSPF process OSPF neighbors Interface configuration Link states Timers Debugging 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Issues Redistributing ANYTHING into OSPF Redistributing OSPF 1 6/1/2018 Valencia Community College Cisco Networking

Valencia Community College Issues Lab closing on 14:00 on Friday. No lab hours on weekends. 6/1/2018 Valencia Community College Cisco Networking