Chapter 1 of 3 · MikroTik MTCINE
BGP
Autonomous systems, sessions, iBGP and eBGP, filters, best path selection, attributes, reflectors and confederations.
- 7topics
- 33 minfast track
- 3diagrams and exhibits
Topics in this chapter
Take them in order, or jump to the one you need.
- 1Autonomous Systems, BGP and the Path Vector AlgorithmLearn what an autonomous system is, why the internet uses BGP between ASes, and how the path vector algorithm uses the AS path to…5 min
- 2BGP Transport, Packet Types, iBGP and eBGPLearn how BGP runs over TCP port 179, the four message types, the session states, and the key behavioural differences between…Diagram5 min
- 3Stub and Non-Stub Scenarios, Private AS RemovalCompare stub and transit autonomous systems, when a customer needs BGP at all, how private AS numbers are removed, and how to…5 min
- 4Multihop Sessions and Loopback PeeringLearn when iBGP and eBGP peers use loopback addresses, how multihop and update source work, and why parallel links need routes to…4 min
- 5BGP Route Distribution and Routing FiltersLearn how routes enter BGP through network statements and redistribution, and how in and out routing filters accept, discard or…5 min
- 6BGP Best Path Selection and Prefix AttributesLearn the order BGP uses to choose a best path and how local preference, AS path prepend, MED, origin and communities are used to…4 min
- 7BGP Route Reflectors and ConfederationsLearn how route reflectors and confederations remove the iBGP full mesh requirement, how reflection rules work, and the settings…Diagram5 min
About this chapter
What this chapter covers
This chapter explains how autonomous systems exchange routes with BGP and how an engineer controls the result on RouterOS.
It starts with the vocabulary, then moves to sessions, policy and finally to scaling inside a large network. Examples use the RouterOS v6 console. Where RouterOS v7 differs, the page says so.
How the topics fit together
The chapter moves from the idea of an AS, through the session, to policy and scale.
Each page builds on the one before it:
- Autonomous systems and path vector give you the vocabulary and the loop rule.
- Transport and packet types show how a session forms, and how iBGP and eBGP differ.
- Stub and non-stub scenarios show where BGP is really needed and how private numbers are removed.
- Multihop and loopback peering show how to keep sessions alive across several links.
- Route distribution and filters show how prefixes enter BGP and how policy is applied.
- Best path and attributes show how the router chooses and how you influence it.
- Reflectors and confederations show how a big AS avoids the full iBGP mesh.
The iBGP rule from the second page explains why the last page exists. Keep it in mind while you read about reflectors.
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.
BGP is best learned with a small lab of three or four virtual routers. Build one session, break it on purpose, and read the peer status. Then add filters one at a time and watch the advertisements change.
Ready for more practice?
The full MikroTik MTCINE question bank has 475 questions, with timed practice exams and an explanation for every answer.
This study guide is independent and is not affiliated with, endorsed by, or sponsored by MikroTik. Vendor names, certification names and exam codes are trademarks of their respective owners and are used for identification only.