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ENARSI 1.10 Troubleshoot OSPF v2/v3

OSPF is a troubleshoot objective, part of the Layer 3 Technologies domain (35% of ENARSI). You already configured simple multi-area OSPF for ENCOR 3.2.b. ENARSI goes deeper: OSPFv3 with both address families, every reason an adjacency can fail, authentication, all network and area types, the LSA types behind them, virtual links and the rules that decide which path wins. Expect exhibit-based questions where you must find the fault from show and debug output, and trouble-ticket simulations where you fix it.

Objective Verb Page
1.10.a Address families (IPv4, IPv6): OSPFv2, OSPFv3 IPv6 and IPv4 address families Troubleshoot OSPFv2, OSPFv3 and Address Families
1.10.b Neighbor relationship and authentication: adjacency requirements, stuck states, MD5, HMAC-SHA, OSPFv3 IPsec Troubleshoot Neighbor Relationships and Authentication
1.10.c (i) Network types: point-to-point, multipoint, broadcast, nonbroadcast Troubleshoot Network Types and DR/BDR
1.10.c (ii) to (iv) Area types, router types, LSA types 1 to 7, virtual link Troubleshoot Areas, Router Types, LSAs and Virtual Links
1.10.d Path preference: intra, inter, E1/E2, N1/N2, cost Troubleshoot Path Preference

Time budget: week 17 of the study plan. Days 1 and 2: address families and adjacency/authentication. Day 3: network types. Days 4 and 5: areas, LSAs and virtual links. Day 6: path preference. Day 7: the practice questions, then the two OSPF simulations under time pressure.

How to study this module

Every page ends with a break/fix lab. Build the baseline, save it, then inject one fault at a time and find it from show output only before you look at the configuration. For each fault write down three things: the symptom, the single command that proved the cause, and the minimal fix. That list is what you bring into the exam.

The diagnostic commands that carry most of this module:

Question you are answering Command
Who are my neighbors and what state are they in? show ip ospf neighbor, show ospfv3 neighbor
What are my local timers, area, network type, cost and authentication? show ip ospf interface [brief], show ospfv3 interface
Why does a neighbor reject my packets? debug ip ospf adj, debug ip ospf hello
Am I an ABR or ASBR, what area types, what reference bandwidth? show ip ospf
Which LSAs exist and who sent them? show ip ospf database [router, network, summary, asbr-summary, external, nssa-external]
Can I reach the ABRs and ASBRs? show ip ospf border-routers
Which route won and why? show ip route <prefix> (type, metric, forward metric)
Is the virtual link up? show ip ospf virtual-links

When you finish, take the OSPF practice questions. Aim for 80% or better before moving on to 1.11 BGP.