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Hi, I'm Iljitsch van Beijnum. These are general neworking-related posts.

My BGP minilab

When I wrote my first BGP book I painstakingly made the config examples on actual Cisco routers. In my opinion, it's crucial to make sure that configuration examples that go in a book actually work.

So when I started writing my new BGP book, I did the same. But this time, I used open source routing software (FRRouting) running in Docker containers. Basically, those containers are very light-weight virtual machines.

This makes it possible to run a dozen virtual routers that start up and shut down in just a few seconds. So it's very easy to run different examples by starting the required virtual routers with the configuration for that example.

This was super useful when I was writing the book.

So I thought it would also be very useful for people reading the book.

So I'm making the "BGP minilab" with all the config examples from the book available to my readers. Download version 2022-11 of the minilab that goes with the first version of the book here.

You can also run the examples in the minilab if you don't have the book. And you can create your own labs based on these scripts.

The minilab consist of four scripts:

There are Mac/Linux shell script and Windows Powershell versions of each script.

Permalink - posted 2022-11-11

Oh SNAP! There is more to Wi-Fi ↔︎ Ethernet than I thought

The tag line for World IPv6 Launch ten years ago was "the future is forever". You know what else seems to be forever? The past. Let's talk about IEEE 802 LLC/SNAP encapsulation.

I always thought when you send IP packets over Wi-Fi, the IP packet would go inside an Ethernet frame, and then the Ethernet frame inside an IEEE 802.11 frame. Turns out this is not how it works: ...

Full article / permalink - posted 2022-07-21

OSPF: time to get rid of the totally not so stubby legacy

Recently, I was looking through some networking certification material. A very large part of it was about OSPF. That's fair, OSPF is probably the most widely used routing protocol in IP networks. But the poor students were submitted to a relentless sequence of increasingly baroquely named features: stub areas, not-so-stubby-areas, totally stubby areas, culminating in totally not-so-stubby areas.

Can we please get rid of some of that legacy? And if not from the standard documents or the router implementations, then at least from the certification requirements and training materials?

Full article / permalink - posted 2022-05-12

The HTTPS and HTTP conundrum

The past few days I have added HTTPS support to bgpexpert.com and iljitsch.com. About ten years ago, I experimented a bit with SSL/TLS (HTTPS) support in Apache, and that was rather difficult.

But no more. Thanks to the efforts of Let's Encrypt and the ACME protocol as implemented in certbot, adding HTTPS support to your websites is now almost ridiculously easy.

Full article / permalink - posted 2021-11-22

→ Software Engineering Radio: Iljitsch van Beijnum on Internet Routing and BGP

I love podcasts. So I'm every happy to be interviewed about BGP on Software Engineering Radio:

Iljitsch van Beijnum, author of the book BGP: Building Reliable Networks with the Border Gateway Protocol https://www.oreilly.com/pub/au/970 discusses internet routing and BGP – the border gateway protocol used by ISPs to update routing information. Host Robert Blumen spoke with Iljitsch about the topology of the internet, autonomous systems (AS), regulatory bodies that coordinate the AS space, IP addresses, the assignment of IPs to ASs; tier-one ISPs, carriers, and home/business ISPs; Internet routing; the path of a packet; routing tables, what they contain, and how they are constructed; routing algorithms; BGP and its role in updating routers with the knowledge of routes held by other routers; and BGP messages. Drill down into the update message. How updates progress from BGP into routing algorithms and then routing tables. What can go wrong. Attacks on BGP.

Permalink - posted 2021-07-13

VLANs on the Mikrotik hAP ac³

For my BGP lab/training setups I have a bunch of routers, real or virtual, that each need several IP addresses to talk to other routers. VLANs are the perfect way to keep all of this manageable: with VLANs, it's possible to have separate IP interfaces, but still just use a single Ethernet port to hook everything up. Simple unmanaged switches simply forward the packets to the right port without looking at the VLAN header, so no need to configure the network.

Until I got my Mikrotik hAP ac³ this week...

Full article / permalink - posted 2021-04-04

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