Whenever we talk about LAN data-link-layer addressing, most engineers automatically switch to the “must be like Ethernet” mentality, assuming all data-link-layer LAN framing must somehow resemble Ethernet frames.

That makes no sense on point-to-point links. As explained in Early Data-Link Layer Addressing article, you don’t need layer-2 addresses on a point-to-point link between two layer-3 devices. Interestingly, there is one LAN technology (that I’m aware of) that got data link addressing right: Fibre Channel (FC).

Julia Evans wrote another great article explaining confusing git terminology. Definitely worth reading if you want to move past simple recipes or reminiscing about old days.

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: