NETWORK FUN-TIMES

It’s official: as of November 2019, I am now JNCIE-SP #2981. And I have the socks to prove it. Click to find out what exam day was like, and whether I think you should take the exam yourself.

A netizen on the world wide web – you know: the information superhighway – reached out to me and some

Hey there: this is part 3 in my series on hub-and-spoke MPLS VPNs! In this post we see the dangers of commands like as-override and independent-domain – and then, we see how to fix the problems they cause. Strap in!

There’s a few different ways of configuring a hub-and-spoke MPLS VPN. In this blog post we learn all about the “one interface” approach. Whether you’re an architect or a student of the JNCIE, you’ll want to know this one inside out!

Hub-and-Spoke VPNs work a little differently than your regular full-mesh MPLS VPN. Want to learn the extra config required for this unique topology? Then click this post for some good learning!

Routing policy in Junos can be a little confusing for beginners – but when it clicks, you’ll see that you can do some truly powerful stuff! Give this post a read to learn all about it!

In this third and final post on Interprovider Option C, we replace LDP with RSVP. Plus, we see the impact of putting BGP-LU in Juniper’s inet.0 table. Put your science hat on, and click here!

In Part 2 of this series we take a look at the label stack in Interprovider Option C. Plus, we look at the use case, and compare it to Option B. Plus: win a trillion pounds! (Not true)

The first in a three-part series explaining Interprovider Option C on Juniper routers! In this post: what is it, and how is it configured? Click here to obtain that 420-69 IQ you’ve always dreamed of.

Traceroute seems such an obvious tool. Who would ever have thought there were so many gotchas? Give this post a read to learn a new one you probably didn’t know!

BGP Labeled-Unicast is the key to making Interprovider Option C work. So, before we learn how to use Option C to extend an MPLS VPn between two ISPs, let’s learn all about this interesting address family. And if you like, we can even hold hands while we learn!

Let’s learn how to stretch an MPLS VPN between ISPs using a thing called “Option B”. It involves a little bit of trust between the ISPs – but as we’ll see, it greatly reduces the complexity in configuration!

Ever wondered whether it’s possible to stretch an MPLS VPN across two ISPs? Well, indeed it is! In fact, there’s three ways to do it, and in this post we learn all about the method officially known as “Option A”.

Today I had the honour of being invited to become a Juniper Ambassador! Click this post to find out exactly what that means for me, for you, and for the future of the planet as we know it…

Hey there: you smell good! That’s probably because you just read Part 1 of this two-part blog post, where we learned all about BGP communities, and how route-targets are used in MPLS VPNs. Well, now you know the theory, let’s look at a problem ticket. Click here to read Part 2!

I fixed a ticket recently that I wanted to share with you, because it hits on three big topics at once: BGP communities, MPLS VPNs, and Junos routing policy. In this first of two posts, we’re going to learn about the theory. Click here to read all about BGP communities!

(DISCLAIMER: This blog post was written at the end of 2018, and was accurate to the JNCIA-Cloud syllabus at the

If you’re thinking about taking Juniper’s excellent Service Provider exam, give this a read – I’ve hooked you up with a ton of useful links!

Regular readers of this blog probably see me as an extremely clever, flawless hunk who knows a lot, never makes mistakes, and is traditionally handsome but with a modern style. And of course, you’re not wrong. Except, here’s the twist: you’re dead wrong.

This is a post about the different ways, and reasons why, we might move prefixes between the inet.3 and inet.0 tables on a Juniper router. You know: like George Clooney does in his spare time. Probably. Don’t look that up.

In this first of a two-part post, I’m going to take you on a magical journey. And by “take you on a magical journey” I mean “teach you what the inet.3 table does on a Juniper router.” Which is basically the same thing as a magical journey, right?

Network engineers often find they need a way to test something, and then take some action if that test fails. Well, you can do these tests oh-so-easily in Junos with a thing called Real-Time Performance Monitoring. RPM is what “other vendors” might call IP SLA. How do they work? Good question, Andrew! Let’s find out.

Imagine a user who says they’re only able to access even-numbered IPs in a destination subnet. “Help!”, they say. “I can’t leave the office until this is fixed, and I need to leave now because my seven large sons require their tri-daily feed of protein shakes. They will whither and die unless I nourish them immediately. The fate of my powerful sons is in your hands, and yours alone.” This exact problem came in to us recently. Well, apart from the bit about the large sons.

This is the third and final part of my whistle-stop tour of IS-IS, for people studying for their Juniper JNCIS-SP and JNCIS-ENT exams. In this post, we learn how to troubleshoot IS-IS. Are you wearing your safety hat? Then, let’s go!

In Part 2 we take a deeper-dive into IS-IS. We do packet captures of LSAs, we look at the metrics, the Designated Intermediate-System, and we even explore our feelings together, so that we can finally find inner-peace with ourselves. Great!!!

Here’s the first of our three-part beginners guide to IS-IS. We’ll compare it to OSPF; we’ll talk about Level 1 and Level 2; we’ll explain the bizarre addressing system; we’ll look at a basic config, and we’ll talk about why Googling for IS-IS is very different from Googling for ISIS.

In the 90s, the big fashion was Tamagotchis. In 2017 it was fidget spinners. And of course, in 2018 there’s only one trend on everyone’s lips: route summarisation. In Junos there’s three ways to summarise routes. Want to know what they are? Well gosh damn, you’ve come to the right place!

Want to learn how to configure Chassis Cluster, which lets you configure high-availability failover on Juniper firewalls? Good luck with the official documentation – it weighs in at precisely 638 pages long. 638 pages! That’s the length of two good books! Or one badly edited one. Anyway, this article is my attempt at boiling those 638 pages down into something a bit more manageable. You can thank me by emailing me £700,000.

Once you’ve read my guide to the new link-state advertisement types in OSPFv3, give this post a read, where we take a deep-deep into the OSPFv3 database. Put your topology hat on: we’re going exploring.

When I first heard that OSPFv3 introduced even more link-state advertisement (LSA) types, I despaired. As if the original seven didn’t take us long enough to memorise! Then I actually learned what they do – and honestly, it’s hard to imagine why we ever did it any differently. Let’s learn about them together!