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 »
If there’s one thing that trips up engineers new to BGP, it’s the difference between eBGP and iBGP. Not because the concept is hard, but because the implications are sneaky. The sessions look the same. The commands are almost identical. But the behavior is different enough to absolutely destroy a network if you’re not paying
eBGP vs iBGP: A Field Guide to Not Confusing Yourself Read More »
Someone on your team suggested BGP. Or you read an article. Or you watched a conference talk where the speaker made it sound like BGP was the answer to everything. And now you’re wondering if your network actually needs it. For most networks, the answer is still no That’s not a knock on BGP, it
Do You Actually Need BGP? (An Honest Answer for People Who Hate Wasting Time) Read More »
Pour something good. This one’s worth it. Border Gateway Protocol, or BGP, has been running the internet since 1989. Your ISP uses it. Amazon uses it. Google uses it. The backbone of every packet that leaves your network and crosses into someone else’s depends on it. And there’s a decent chance you’ve been avoiding it
BGP: The Protocol That Runs the Internet (Whether You Like It or Not) Read More »
A Network Architect’s Guide to Diagnosing Problems Before They Become Resume-Generating Events Welcome to the grand finale.You’ve survived the theory, the design, the LSAs, the SPF math, and the war stories.Now it’s time for the part every network engineer eventually faces: Troubleshooting OSPF when it decides to set itself on fire at 2:13 AM. This
Troubleshooting OSPF Without Crying (Much) Read More »
Because Good OSPF Design Prevents 2 A.M. Phone Calls, Heartburn, and Existential Dread You’ve stuck with this series through neighbor states, areas, LSAs, and SPF algorithms.Now we get to the part where all that knowledge turns into real-world design wisdom—the kind you only gain from:• production outages,• painful migrations,• and explaining to leadership why OSPF
OSPF Design Tips: Lessons From the Field (and the Outages) Read More »
Where We Finally Explain How OSPF Actually Chooses a Path—Without Math Trauma You’ve made it to Post 5—congratulations. At this point, you know more about OSPF than the average person knows about their own taxes. Now we finally lift the hood and look at the part of OSPF that actually makes decisions: SPF — the
SPF Algorithm: Dijkstra, the Network’s Reluctant Matchmaker Read More »
Because Nothing Says ‘Fun Weekend’ Like Memorizing LSA Types If you’ve made it this far in OSPF, you’re doing better than most.You’ve survived neighbor states.You’ve survived areas.Now it’s time for the part of OSPF that everyone pretends to fully understand during design meetings: LSAs — Link State Advertisements OSPF’s postal service, rumor mill, and gossip
LSAs Explained: The OSPF Postal Service Read More »