Nine episodes. Thirteen-plus blog posts. A lot of bourbon. If you’ve followed the Bourbon & BGP series from the beginning, you’ve covered the full foundation of BGP. Not the survey-level “BGP is an EGP protocol that uses TCP port 179” kind of coverage. The real stuff. The stuff that actually matters when you’re building networks
BGP From Zero to Route Reflector: What We Covered and Where to Go Next Read More »
Here’s something that surprises people who are new to BGP. The same protocol that’s been routing IPv4 across the internet since 1994 also handles IPv6, MPLS VPNs, EVPN, multicast routing information, and several other things you might not expect. Not through separate protocols. Through address families. Once you understand address families, BGP stops being “that
BGP Address Families: One Protocol, Many Tables, Infinite Confusion Read More »
If you mention BGP confederations in a group of network engineers, you’ll get a split reaction. Some people will immediately recognize what they are and nod knowingly. Others will tilt their head slightly like a dog that heard a strange sound. Both reactions are completely reasonable. Confederations solve the same problem as route reflectors, which
BGP Confederations Explained: The Dark Art of Splitting Your AS Read More »
Here’s the scenario. You configure iBGP between your edge routers and your internal routers. Sessions come up. You see routes in the BGP table. Everything looks right. And then you ping a destination that should be reachable and it fails. show bgp ipv4 unicast x.x.x.x/y shows the route. show ip route x.x.x.x shows the route in the routing
What Is Next-Hop Self and Why Is It the First Thing You Break? Read More »
You just finished reading about the iBGP full mesh problem. You understand the math. You know why full mesh doesn’t scale. Route reflectors are the solution most networks actually use. They’re not complicated once you understand what problem they’re solving and how the loop prevention works. But implement them without understanding those two things and
Route Reflectors: The BGP Feature That Saved Your Sanity (Eventually) Read More »
Reading about BGP and configuring BGP are two different things. Theory gives you a mental model. Configuration gives you the humbling experience of staring at a neighbor that won’t come up while everything looks correct. This is the post that gets you from zero to a working eBGP session with proper route filtering. The commands
Your First eBGP Config (That Won’t Embarrass You at the Next Peer Review) Read More »
You’ve been reading about BGP. You understand what it does. You have a rough handle on path selection and the difference between eBGP and iBGP. Now someone in your organization is asking whether your network needs BGP, or maybe you’re the one asking. Let’s settle this properly. The answer is almost always simpler than people
You’ve Read the Docs, Now Be Honest: Does Your Network Actually Need BGP? Read More »
BGP path selection is the thing people memorize for certification exams and then forget the moment the cert is in hand. Don’t do that. BGP best path is the algorithm that actually decides which route your traffic takes. If you don’t understand it, you can’t troubleshoot it. And when something breaks at 2am, you’ll be
BGP Best Path Selection: A Step-by-Step Guide for People Who Learn by Suffering Read More »
Before two routers can run BGP together, they need identities. Not usernames and passwords, though those exist too. What BGP actually cares about is the autonomous system number. That ASN is the foundation of how BGP figures out where routes came from, whether they’re legitimate, and how to prevent loops. If you’ve glossed over ASNs
ASNs Explained: Public, Private, and Why 64512 Might Be Your New Best Friend Read More »
Everything in networking has a cost. Sometimes it’s bandwidth. Sometimes it’s processing overhead. With iBGP, the cost is session count, and it gets ugly fast. If you’ve spent any time with BGP documentation, you’ve heard the phrase “full mesh.” If you haven’t, you’re about to. And once you understand why it’s required and what it
The iBGP Full Mesh Problem: Or, Why Your Brain Will Hurt Later Read More »