Course contents

BGP

BGP from the first session to the decisions that move traffic: how BGP routers peer, how eBGP and iBGP differ, how the best path is chosen, how to filter and steer routes, and how to find faults. The six modules follow BGP topic 1.11 of Cisco's ENARSI 300-410 exam and eBGP in ENCOR 350-401.

Advanced · 43 lessons

Covers eBGP and iBGP, Neighbour states, Best-path selection, Route maps and filtering, Route reflectors and Troubleshooting.

The course uses one network throughout: a company in AS 64500 with two routers, R1 and R2, each connected to a different internet provider. The company advertises its own address block, 198.51.100.0/24, to both. It assumes CCNA-level routing; the BGP overview in the CCNA Routing course is a short introduction if BGP is completely new.

192.0.2.0/30192.0.2.4/30Gi0/1 .1.2 Gi0/110.0.12.0/30Gi0/2Gi0/2InternetISP AAS 64501ISP BAS 64502R1RID 1.1.1.1R2RID 2.2.2.2Company LAN, AS 64500Subnet 198.51.100.0/24

Device key: ISP A, ISP B, R1, R2 (router) · Company LAN, AS 64500 (network / site)

Lines show the example’s network connections. Thick links: uplinks/WAN, as labelled. Read the numbered steps for traffic direction and changes.

Reading the addresses

IP labels identify interfaces or destinations. Subnet labels identify networks; /n is the prefix length. A router ID (RID) identifies a routing process and need not be a reachable interface.

An IP address alone is not a URL. A web URL includes a scheme such as https://; an address on a router or printer does not imply a website.

  • ISP A: AS 64501
  • ISP B: AS 64502
  • R1: RID 1.1.1.1
  • R2: RID 2.2.2.2
  • Company LAN, AS 64500: Subnet 198.51.100.0/24
  1. 1. eBGP to each ISP: R1 peers with ISP A and R2 with ISP B, across their autonomous system borders.
  2. 2. iBGP inside AS 64500: R1 and R2 share what each learned from its ISP.
  3. 3. One prefix, two ways in: Both ISPs carry the company's block to the rest of the internet.

What's in this course

6 modules · 43 lessons · about 9 hours of reading

Module 1: BGP Foundations

Autonomous systems, why the internet routes with BGP, how two BGP routers form a session, and how eBGP and iBGP differ.

Module 2: Configuring BGP

eBGP to two ISPs, iBGP between the company's own routers, IPv6 address families and a first lab.

Module 3: Path Selection

The attributes BGP compares, the order it compares them in, and how to steer traffic in and out.

Module 4: BGP Policy

Filtering what you send and accept, and changing attributes with route maps.

Module 5: Scaling and Operations

Route reflectors, peer groups, authentication, timers and private AS numbers, and BGP in a VRF.

Module 6: Troubleshooting and Practice

A method for BGP faults, tickets to diagnose, a revision sheet and a test.

Start the first lesson →