Chapter 1 of 4 · Cisco CCNP 300-410 ENARSI
Layer 3 Technologies
Distance, route maps, redistribution, VRF-Lite, BFD, EIGRP, OSPF and BGP troubleshooting.
- 8topics
- 42 minfast track
- 8diagrams and exhibits
- 35%of the exam
Topics in this chapter
Take them in order, or jump to the one you need.
- 1Administrative Distance and Loop PreventionLearn how administrative distance picks between routing sources, how floating static routes work, and how split horizon…5 min
- 2Route Maps and Policy Based RoutingLearn how route maps match and change routes, where they attach in routing protocols, and how policy based routing sends traffic…Diagram5 min
- 3Redistribution and SummarizationLearn how to redistribute routes between OSPF, EIGRP, RIP and BGP, set seed metrics, avoid loops, and use manual and automatic…Diagram5 min
- 4VRF-Lite and Bidirectional Forwarding DetectionLearn how VRF-Lite builds separate routing tables on one router, how to configure and verify it on IOS XE, and how BFD detects…Diagram5 min
- 5Troubleshooting EIGRPTroubleshoot EIGRP in classic and named mode for IPv4 and IPv6: neighbour rules, authentication, DUAL terms, stubs, variance and…5 min
- 6Troubleshooting OSPFv2 and OSPFv3Troubleshoot OSPF neighbours, authentication, network types, area types, router types, virtual links and path preference for…Diagram5 min
- 7BGP Neighbour RelationshipsTroubleshoot BGP sessions for eBGP and iBGP: states, timers, multihop, next hop, authentication, 4 byte AS, peer groups and…Diagram6 min
- 8BGP Path Selection, Route Reflectors and PolicyLearn the BGP best path order, how a single route reflector works, and how inbound and outbound filtering and attribute changes…Diagram6 min
About this chapter
What this chapter covers
Layer 3 Technologies is about how routers learn, choose and control routes, and how you find the fault when the result is wrong.
The chapter starts with the rules that apply to every routing source, such as administrative distance and route maps. It then moves to the three main protocols: EIGRP, OSPF and BGP.
The emphasis is on troubleshooting. You are expected to read output, spot the mismatch and know which command fixes it.
How the topics fit together
Every routing protocol feeds the routing table, and the general tools decide what ends up there.
The general topics come first:
- Administrative distance and loop prevention explain which source wins and how loops are stopped.
- Route maps and policy based routing show how to match and change routes, and traffic.
- Redistribution and summarization join protocols together and shrink the tables.
- VRF-Lite and BFD separate routing tables and speed up failure detection.
The protocol pages then use those tools in context. EIGRP and OSPF are interior protocols with their own neighbour rules and path logic. BGP has two pages, one for the neighbour session and one for path selection and policy.
Most protocol faults come down to a neighbour that did not form or a route that was filtered. Check the session first, then the policy.
How to use these pages
Each topic page has the same shape, so you can skim for what you need.
- What it is: the idea in plain words.
- How it works: the mechanism, with diagrams and example commands.
- What to remember for the exam: the facts to memorise.
- Common mistakes: the classic traps.
- Check yourself: three questions to test your understanding.
Commands are shown for IOS XE unless the page says otherwise. Practise in a lab. Break a neighbour on purpose, such as a wrong timer or key, and see which show command reveals it.
Ready for more practice?
The full Cisco CCNP 300-410 ENARSI question bank has 857 questions, with timed practice exams and an explanation for every answer.
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