At least some people learn from others’ mistakes: using the concepts proven by some well-publicized BGP leaks, malicious actors quickly figured out how to hijack BGP prefixes for fun and profit.

Fortunately, those shenanigans wouldn’t spread as far today as they did in the past – according to RoVista, most of the largest networks block the prefixes Route Origin Validation (ROV) marks as invalid.

Notes:

• ROV cannot stop all the hijacks, but it can identify more-specific-prefixes hijacks (assuming the origin AS did their job right).
• You’ll find more Network Security Fallacies videos in the How Networks Really Work webinar.

Last time we built a network with two adjacent BGP routers. Now let’s see what happens when we add a core router between them:

Almost exactly a decade ago I wrote about a paper describing how IBGP migrations can cause forwarding loops and how one could reorder BGP reconfiguration steps to avoid them.

One of the paper’s authors was Laurent Vanbever who moved to ETH Zurich in the meantime where his group keeps producing great work, including the Chameleon tool (code on GitHub) that can tame transient loops while reconfiguring BGP. Definitely something worth looking at if you’re running a large BGP network.

It’s time for a Halloween story: imagine the scary scenario in which a DHCP client asks for an address, gets it, and then immediately declines it. That’s what I’ve been experiencing with vJunos Evolved release 23.2R1.15.

My good friend Tiziano Tofoni finally created an English version of his evergreen classic BGP from theory to practice with co-authors Antonio Prado and Flavio Luciani.

I had the Italian version of the book since the days I was running SDN workshops with Tiziano in Rome, and it’s really nice to see they finally decided to address a wider market.

Also, you know what would go well with that book? Free open-source BGP configuration labs of course 😉

After covering the theoretical part of network addressing (part 2, part 3), let’s go into some practical examples. I’ll start with data link layer and then move on to networking and higher layers.

The earliest data link implementations that were not point-to-point links were multi-drop links and I mentioned them in the networking challenges part of the webinar. Initially, we implemented multi-drop links with modems, but even today you can see multi-drop in satellite communications, Wi-Fi, or in cable modems.

Here’s a quick update on the BGP Labs project status: now that netlab release 1.6.4 is out, I could remove the dependency on using Cumulus Linux as the external BGP router.

You can use any device that is supported by bgp.session and bgp.policy plugins as the external BGP router. You could use Arista EOS, Aruba AOS-CX, Cisco IOSv, Cisco IOS-XE, Cumulus Linux or FRR as external BGP routers with netlab release 1.6.4, and I’m positive Jeroen van Bemmel will add Nokia SR Linux to that list.

If you’re not ready for a netlab upgrade, you can keep using Cumulus Linux as external BGP routers (I’ll explain the behind-the-scenes magic in another blog post, I’m at the Deep Conference this week).

For more details, read the updated BGP Labs Software Installation and Lab Setup guide.

Features in netlab release 1.6.4 were driven primarily by the needs of my BGP labs project:

• bgp.session plugin (formerly known as ebgp.utils plugin) got support for BFD, passive BGP peers and remove-private-as option.
• bgp.policy plugin implements basic BGP routing policy tools, including per-neighbor weights, local preference and MED.
• You can enable external tools in user defaults and use default groups to create user- or project-wide groups in the defaults files.
• Version-specific lab topology files allow netlab to select a lab topology that is a best fit for the netlab release you’re running.

Numerous platforms already support the new BGP nerd knobs:

I’ll be talking about Internet routing security at the Deep conference in a few days, and just in case you won’t be able to make it¹ ;) here’s the first bit of my talk: a very brief history of BGP route leaks².

Note: you’ll find more Network Security Fallacies videos in the How Networks Really Work webinar.

After going through the BGP basics, it’s time to build a network that has more than one BGP router in it, starting with the simplest possible topology: a site with two WAN edge routers.

TL&DR: Violating the Betteridge’s Law of Headlines, the answer is “Yes, but the devil is in the details.”

It all started with the following observation by Minh Ha left as a comment to my previous BGP session security blog post:

I’d think it’d be obvious for BGP routers to only accept incoming sessions from configured BGP neighbors, right? Because BGP is the most critical infrastructure, the backbone of the Internet, why would you want your router to accept incoming session from anyone but KNOWN sources?

Following my “opinions are good, facts are better” mantra, I decided to run a few tests before opinionating¹.

Bruce Schneier wrote a thoughtful article on the various perceptions of AI Risks including this gem:

As the science-fiction author Ted Chiang has said, fears about the existential risks of AI are really fears about the threat of uncontrolled capitalism, and dystopias like the paper clip maximizer are just caricatures of every start-up’s business plan.

Enjoy!

A few days after I published the EBGP session protection lab, Jeroen van Bemmel submitted a pull request that added TCP-AO support to netlab. Now that the release 1.6.3 is out, I could use it to build the Protect BGP Sessions with TCP Authentication Option (TCP-AO) lab exercise.

netlab release 1.6.3 added numerous BGP nerd knobs:

• You can create EBGP multihop sessions in the global routing table when using Arista EOS, Cisco IOSv, Cisco IOS-XE, FRR and Cumulus Linux 4.x.
• ebgp.utils plugin supports TCP-AO, configurable BGP timers, and Generic TTL Security Mechanism (TTL session protection)
• BGP neighbor reports hide irrelevant columns.

We also:

I encountered several articles explaining the challenges of simulating your network in a virtual lab in the last few months, including:

• Some thoughts on digital twins by Jeff McLaughlin
• Network Simulation is hard – Part 1, Part 2 – by Pete Crocker
• Twenty-five open-source network emulators and simulators you can use in 2023 by Brian Linkletter

Enjoy!