ENARSI 1.1 to 1.5 Routing Control¶
Routing control is about deciding which routes a router believes, which routes it passes on, and in what form. It is the part of ENARSI's Layer 3 domain (35% of the exam) that cuts across every protocol: administrative distance, route maps and filters, loop prevention, redistribution and summarization apply equally to EIGRP, OSPF, RIP and BGP. Every objective here is troubleshoot. Expect exhibits of show ip route, show ip protocols, show route-map and topology or LSDB output, where you must find the one line that explains a missing route, a suboptimal path or a loop, and choose the smallest fix.
| Objective | Verb | Page |
|---|---|---|
| 1.1 Administrative distance (all routing protocols) | Troubleshoot | Administrative Distance |
| 1.2 Route maps for any routing protocol: attributes, tagging, filtering; prefix lists and distribute lists | Troubleshoot | Route Maps and Filtering |
| 1.3 Loop prevention: filtering, tagging, split horizon, route poisoning | Troubleshoot | Loop Prevention |
| 1.4 Redistribution between any routing protocols or routing sources | Troubleshoot | Redistribution |
| 1.5 Manual and auto-summarization with any routing protocol | Troubleshoot | Summarization |
How the pages connect. AD (1.1) decides which copy of a route a boundary router installs. Route maps and tags (1.2) are the tools you use to filter and mark routes. Loop prevention (1.3) explains the built-in protections and why redistribution needs your own. Redistribution (1.4) brings all three together in the two-point mutual redistribution problem, the single most likely complex scenario in this domain. Summarization (1.5) changes what is advertised and adds the Null0 discard route.
Every page ends with a break/fix lab on IOSv in CML. Save a baseline, inject the faults listed, and fix them using only show commands to find the cause.
Time budget: week 14 of the study plan for 1.1 to 1.4, and the first two days of week 15 for 1.5. Suggested split:
| Day | Work |
|---|---|
| Week 14, days 1 and 2 | Administrative distance and route maps, with both labs |
| Week 14, day 3 | Loop prevention and the DMVPN split horizon lab |
| Week 14, days 4 to 6 | Redistribution, the two-point lab, then Sim 05 against the clock |
| Week 15, days 1 and 2 | Summarization and its lab, then the practice questions |
Related material:
- Diagrams: N01 Administrative distance, N02 Two-point redistribution feedback, N03 Fixing feedback with tags, N04 Route-map processing, N05 Summarization points
- Simulations: Sim 05, mutual redistribution, a loop and tags; Sim 07, BGP path selection policy for route maps applied to BGP
- Question bank: ENARSI bank part 1, questions 1 to 14
When you finish, take the Routing Control practice questions. Aim for 80% or better before moving on.
Unlock the full question banks and cram sheets
A free account opens every question bank, the timed practice exams, the printable cram sheets, all the simulations and the lab files. Without one you see a 5-question sample of each.
No card needed. Study tips by email are optional and off unless you tick the box. Your address is never sold or shared. Privacy policy ยท Terms
Signed in as . Your account
You're on the free account, so lessons after the first module, question banks, exams and cram sheets show a sample. See Track Pass and All-Access
Also from NetManager Systems: NetManager, network monitoring for multi-vendor networks. Try the NetManager, NetDiag, PCAP Analyzer and OpsDash demos: every new account gets a free 7-day read-only login to each.