Understand Open Shortest Path First (ospf) Design Guide

ip subnet-zero
command on the router in order to resolve this issue.
RTA#
ip subnet-zero
interface Ethernet2
ip address 192.168.0.10 255.255.255.128
interface Ethernet3
ip address 192.168.0.160 255.255.255.192
interface Ethernet4
ip address 192.168.0.226 255.255.255.192
RTA#show ip route connected
192.168.0.0 is variably subnetted, 3 subnets, 2 masks
C 192.168.0.0 255.255.255.128 is directly connected, Ethernet2
C 192.168.0.128 255.255.255.192 is directly connected, Ethernet3
C 192.168.0.192 255.255.255.192 is directly connected, Ethernet4
Related Information

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Cisco IOS® IP Routing: OSPF Command Reference
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OSPF and MTU
●
OSPF neighbors are stuck in exstart and exchange state due to MTU mismatch
●
OSPF Support Page
●
OSPF: Frequently Asked Questions
●
Technical Support & Documentation - Cisco Systems
●

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Document Outline

• Understand Open Shortest Path First (OSPF) - Design Guide
  • Contents
  • Introduction
  • Background Information
    • OSPF versus RIP
    • What Do We Mean by Link-States?
  • Shortest Path First Algorithm
    • OSPF Cost
    • Shortest Path Tree
  • Areas and Border Routers
  • Link-State Packets
  • Enable OSPF on the Router
  • OSPF Authentication
    • Simple Password Authentication
    • Message Digest Authentication
  • The Backbone and Area 0
  • Virtual Links
    • Areas Not Physically Connected to Area 0
    • the Backbone
  • Neighbors
  • Adjacencies
    • DR Election
    • Build the Adjacency
    • Adjacencies on Point-to-Point Interfaces
    • Adjacencies on Non-Broadcast Multi-Access (NBMA) Networks
  • Avoid DRs and neighbor Command on NBMA
    • Point-to-Point Subinterfaces
    • Select Interface Network Types
  • OSPF and Route Summarization
    • Inter-Area Route Summarization
    • External Route Summarization
  • Stub Areas
  • Redistribute Routes into OSPF
    • E1 vs. E2 External Routes
  • Redistribute OSPF into Other Protocols
    • Use of a Valid Metric
    • VLSM
    • Mutual Redistribution
  • Inject Defaults into OSPF
  • OSPF Design Tips
    • Number of Routers per Area
    • Number of Neighbors
    • Number of Areas per ABR
    • Full Mesh vs. Partial Mesh
    • Memory Issues
  • Summary
  • Appendix A: Link-State Database Synchronization
    • Link-State Advertisements
    • OSPF Database Example
  • Appendix B: OSPF and IP Multicast Address
  • Appendix C: Variable Length Subnet Masks (VLSM)
  • Related Information