Latest:
  • Your “Multihop” BGP Session Probably Isn’t Multi-Hop
  • A Beginners Guide to Junos Firewall Filters
  • How to Increase the CLI Character Limit in Junos
  • Route Distinguishers: The Secret To Load Balancing In Multihomed MPLS VPNs
  • Junos: IS-IS Study Notes, Part 5 – Troubleshooting (For JNCIS-SP and JNCIS-ENT Students)
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LATEST POSTS

Your “Multihop” BGP Session Probably Isn’t Multi-Hop
bgp jncis juniper junos routing security 

Your “Multihop” BGP Session Probably Isn’t Multi-Hop

December 29, 2022 Chris 5

BGP study guides tell you that loopback-to-loopback EBGP session require a TTL of 2 or more. The trouble is, they rarely say why. This leads new students to come to some very incorrect assumptions about how the TTL field works in IP. In fact though, you can absolutely have a TTL of 1! In this post we clear up all the confusion – and we even look at how you can use a TTL of 255 to bring extra security to your network.

A Beginners Guide to Junos Firewall Filters
security 

A Beginners Guide to Junos Firewall Filters

October 7, 2022 Chris 0

Firewall filters in Junos let you do far more than just filter traffic. They’re really powerful! And, despite their length, you can create them very quickly and easily. Let me show you how!

How to Increase the CLI Character Limit in Junos
juniper junos junos for ios engineers 

How to Increase the CLI Character Limit in Junos

September 25, 2022 Chris 0

Networking devices like Junos will cut off your CLI input if you type too much. But did you know there’s an easy fix? Let me show you.

Route Distinguishers: The Secret To Load Balancing In Multihomed MPLS VPNs
bgp juniper junos mpls routing vpn 

Route Distinguishers: The Secret To Load Balancing In Multihomed MPLS VPNs

June 7, 2022 Chris 0

There’s three types of route distinguisher – and one of them unlocks some seriously useful advantages. If you don’t know how to use route distinguishers for load balancing inside an MPLS VPN, then this post is for you. Junos config, but vendor-neutral theory. Give it a read!

Junos: IS-IS Study Notes, Part 5 – Troubleshooting (For JNCIS-SP and JNCIS-ENT Students)
isis jncis juniper junos 

Junos: IS-IS Study Notes, Part 5 – Troubleshooting (For JNCIS-SP and JNCIS-ENT Students)

April 14, 2022 Chris 0

It’s the fifth and final part of our lessons on IS-IS! You’re now ready to learn how to troubleshoot and verify everything you’ve done so far. You’re really close to the finish line, so don’t give up!

You’re Probably Using The Term MPLS Wrong
mpls vpn 

You’re Probably Using The Term MPLS Wrong

April 5, 2022 Chris 3

Is this title clickbait? I don’t think so – because once upon a time, I did exactly the same thing, and it cost me a job! Well, don’t worry: I’m here to help you avoid making the same mistake. Click here to find out my wild story, and how you can bring some commendable precision to your conversations about networking.

MPLS Segment Routing, Part 2: Junos Config!
isis junos mpls ospf segment routing 

MPLS Segment Routing, Part 2: Junos Config!

January 30, 2022 Chris 0

It’s time to learn how to configure MPLS segment routing in Junos! In this second part of my ongoing series I show you how easy it is to use SR as a replacement for LDP. The config is easy, and you’ll be itching to do it by the time you read this post.

MPLS Segment Routing, Part 1: The Theory (Beginner’s Guide)
isis mpls ospf segment routing 

MPLS Segment Routing, Part 1: The Theory (Beginner’s Guide)

January 22, 2022 Chris 6

Every year, more folks are talking abouts segment routing for MPLS. Want to know what the fuss is about? Start here! This post gives you the high-points of some of the most important parts of the theory. Node SIDs, Adjacency SIDs, traffic-engineered LSPs, shortest path LSPs, and more are covered here. Read it and level up!

How To Read A Junos Class-Of-Service Configuration
class-of-service juniper junos 

How To Read A Junos Class-Of-Service Configuration

November 30, 2021 Chris 4

Struggling to read Junos Class-of-Service config? This post is for you: it shows you where to start, what order to read each piece in, and what to look for. After this you’ll have no problem working out exactly what’s going on!

A COMPLETE BEGINNER’S GUIDE TO SUBNETTING
routing subnetting 

A COMPLETE BEGINNER’S GUIDE TO SUBNETTING

November 13, 2021 Chris 11

If you’re a newcomer to networking, chances are you’re struggling to get your head around subnet masks. Well don’t worry: your goth uncle is here to explain how it all works. CCNA and JNCIA/JNCIS students, click here for some cool new knowledge!

Junos: IS-IS Study Notes, Part 4 – Levels, Areas, The Attached Bit, and Default Routes
isis jncis juniper junos 

Junos: IS-IS Study Notes, Part 4 – Levels, Areas, The Attached Bit, and Default Routes

October 11, 2021 Chris 1

The fourth part in this intro to IS-IS series tackles areas, and how they’re different to levels. A lot of new students confuse them, and a lot of documentation gets it wrong too! This post clears everything up for you, and will make you super confident. You’ll also learn about IS-IS default routes, and route leaking from L2 to L1. Give it a click!

WHY IS 65535 NOT PART OF THE PRIVATE AUTONOMOUS SYSTEM RANGE?
bgp 

WHY IS 65535 NOT PART OF THE PRIVATE AUTONOMOUS SYSTEM RANGE?

September 28, 2021 Chris 1

A lot of websites tell you that the private AS range is 64512 to 65535. However, this isn’t quite correct – and the reason is really interesting. Click here to go on a BGP journey with me!

CLEAN UP YOUR ROUTING TABLE! REMOVING POINT-TO-POINT SUBNETS FROM IS-IS, IN JUNOS
isis jncis juniper junos routing 

CLEAN UP YOUR ROUTING TABLE! REMOVING POINT-TO-POINT SUBNETS FROM IS-IS, IN JUNOS

September 20, 2021 Chris 2

Some ISPs like to remove point-to-point prefixes from IS-IS. This keeps their routing tables small and easier to read. But how does it work? Doesn’t this break things? What are the trade-offs? This post shows you how to configure this solution, and the things you’ll want to consider if you deploy it. It’s super-cool, and you’ll definitely enjoy seeing the mechanics in action!

FIVE BRILLIANT JUNOS TIME-SAVERS YOU MIGHT NOT KNOW ABOUT
jncia junos 

FIVE BRILLIANT JUNOS TIME-SAVERS YOU MIGHT NOT KNOW ABOUT

September 12, 2021 Chris 5

Junos is packed full of CLI time-savers that you might not know about. Copying config, renaming, hiding, and saving config – there’s plenty you can do with one single command, when you know how. Give this post a read to find out how to turn your job from a chore into a joy!

SNMP OID: THOSE RANDOM NUMBERS ACTUALLY MEAN SOMETHING!
juniper junos snmp troubleshooting 

SNMP OID: THOSE RANDOM NUMBERS ACTUALLY MEAN SOMETHING!

July 10, 2021 Chris 0

I bet you’ve looked at SNMP Objects like 1.3.6.1.2.1.2.2.1.7 and wondered what on earth it means. Well, let me satisfy your curiosity: by the end of this post you’ll learn how to find SNMP objects to monitor anything you can think of, and you’ll even learn how to know what this number means by sight!

RSVP: CREATING MPLS LSPs IN JUNOS (FOR JNCIS-SP STUDENTS)
jncis juniper junos mpls 

RSVP: CREATING MPLS LSPs IN JUNOS (FOR JNCIS-SP STUDENTS)

July 4, 2021 Chris 2

In this post we show how to configure RSVP in Junos – and then we roll up our sleeves to look at some packet captures of the PATH and RESV messages on the wire. There’s some mighty fine learning in this post!

What is MPLS? A Beginners Explanation, For Network Engineers
jncis juniper junos mpls routing 

What is MPLS? A Beginners Explanation, For Network Engineers

April 22, 2021 Chris 6

I recently received an email from someone asking if I knew a good complete beginners guide to MPLS. Their mail inspired me, so I wrote one for them – and now, I’m sharing it with you! If you’ve always wanted to know what MPLS is, click here to fulfill your deepest dreams.

L2VPN: THE LABEL BASE AND OFFSET, EXPLAINED!
bgp juniper junos mpls routing vpn 

L2VPN: THE LABEL BASE AND OFFSET, EXPLAINED!

February 13, 2021 Chris 4

Pseudowires are easy on the surface – but dig a bit deeper, and there’s some interesting complexity. Click here to learn the details about BGP-signalled L2VPNs!

MAXIMISE YOUR JUNOS NETWORK WITH MPLS, PART 3: CONTAINER LSPs
juniper junos mpls 

MAXIMISE YOUR JUNOS NETWORK WITH MPLS, PART 3: CONTAINER LSPs

February 2, 2021 Chris 1

Container LSPs let us automatically create MPLS LSPs when we need them, and tear them down when we don’t. We can automate load-balancing, and keep the state in our network to a minimum. It’s really nice! Click here to read all about them, in the third and final part of this series on MPLS bandwidth, and automating our network to get the most out of it.

MAXIMISE YOUR JUNOS NETWORK WITH MPLS, PART 2: AUTO-BANDWIDTH
juniper junos mpls 

MAXIMISE YOUR JUNOS NETWORK WITH MPLS, PART 2: AUTO-BANDWIDTH

January 10, 2021 Chris 1

Setting RSVP bandwidth reservations automatically is very prone to error. Luckily, there’s a better way: we can automate the whole thing using the Junos auto-bandwidth command. Let’s take a look at some cool new Juniper config!

MAXIMISE YOUR JUNOS NETWORK WITH MPLS, PART 1: RSVP BANDWIDTH & PRIORITIES
isis juniper junos mpls routing 

MAXIMISE YOUR JUNOS NETWORK WITH MPLS, PART 1: RSVP BANDWIDTH & PRIORITIES

December 14, 2020 Chris 5

RSVP lets us create LSPs that reserve bandwidth in advance. And that’s exactly what this three-part blog post series is all about! In this first post we’re going to learn how we combine bandwidth and priorities to get the most out of the bandwidth in our network. Click here for good times!

JUNOS: MPLS SELF-PING, ON JUNIPER ROUTERS
juniper junos mpls troubleshooting 

JUNOS: MPLS SELF-PING, ON JUNIPER ROUTERS

December 6, 2020 Chris 8

If you’re an ISP running Juniper, it’s essential that you allow MPLS Self-Ping. If you don’t… weird things happen. Click to find out more!

BFD ON JUNOS! BIDIRECTIONAL FORWARDING DETECTION – JUNIPER-CONFIG, MULTI-VENDOR EXPLANATION!
jncis juniper junos routing 

BFD ON JUNOS! BIDIRECTIONAL FORWARDING DETECTION – JUNIPER-CONFIG, MULTI-VENDOR EXPLANATION!

September 12, 2020 Chris 2

BFD is a protocol that gives all your other protocols sub-second failure detection times. Very useful! This blog post uses Junos config, but the explanation is multi-vendor. Give it a read!

JUNIPER JNCIP-SP: USING INDEPENDENT-DOMAIN TO TUNNEL CUSTOMER BGP VPN PREFIXES
bgp juniper junos mpls vpn 

JUNIPER JNCIP-SP: USING INDEPENDENT-DOMAIN TO TUNNEL CUSTOMER BGP VPN PREFIXES

August 22, 2020 Chris 1

The independent-domain command is a little-known but big-useful command. Let’s see how we can use it in Junos to tunnel localpref info from one VPN customer site to another!

REDISTRIBUTING YOUR ENTIRE IS-IS NETWORK BY MISTAKE: BEWARE THIS DEFAULT BEHAVIOUR!
isis junos 

REDISTRIBUTING YOUR ENTIRE IS-IS NETWORK BY MISTAKE: BEWARE THIS DEFAULT BEHAVIOUR!

July 21, 2020 Chris 2

If you leave IS-IS to its default config, you could cause something big to impact your network! And chances are, even if you think you know what that impact is, you might not have worked out the whole story. Click here to read the lesson I learned in my lab!

JUNOS FOR CISCO IOS ENGINEERS: SAVING YOUR CONFIG – WITH POWER!
junos for ios engineers 

JUNOS FOR CISCO IOS ENGINEERS: SAVING YOUR CONFIG – WITH POWER!

July 6, 2020 Chris 5

In Part 3 of this, we see how Junos takes saving configurations to the next level, and gives us HUGE power. Checking our work, rolling back to older configs, automatically rolling back to fix problem – we can do so much with Junos. Let’s find out how!

ROUTE DISTINGUISHERS vs ROUTE TARGETS: WHAT’S THE DIFFERENCE? (JUNOS FOR CISCO IOS ENGINEERS)
bgp jncis juniper junos junos for ios engineers mpls routing vpn 

ROUTE DISTINGUISHERS vs ROUTE TARGETS: WHAT’S THE DIFFERENCE? (JUNOS FOR CISCO IOS ENGINEERS)

May 10, 2020 Chris 19

In this post we use both Cisco IOS and Juniper Junos config to see the difference between route-distinguishers and route-targets in MPLS VPNs. Why do we need both of them? Click here to find out!

JUNOS FOR IOS ENGINEERS: HOW DO YOU CONFIGURE A JUNOS ROUTER?
jncia juniper junos junos for ios engineers ospf 

JUNOS FOR IOS ENGINEERS: HOW DO YOU CONFIGURE A JUNOS ROUTER?

May 4, 2020 Chris 2

In Part 2 of this series we look at how you make configuration changes in Junos – and how you can very easily scrap your changes without doing any damage o your network. Very clean!

USING PYTHON TO CREATE 12,000 LINES OF JUNIPER SRX CONFIG IN 0.01 SECONDS
juniper junos python 

USING PYTHON TO CREATE 12,000 LINES OF JUNIPER SRX CONFIG IN 0.01 SECONDS

April 5, 2020 Chris 8

This post assumes ZERO Python knowledge on your part! You don’t even need Junos knowledge: I’ll do my best to make this useful for folks of ALL skill levels. If you’ve ever wanted to learn Python, but never knew where to start… read on!

JUNOS FOR IOS ENGINEERS: HOW DO I READ A JUNOS CONFIG?
junos junos for ios engineers ospf 

JUNOS FOR IOS ENGINEERS: HOW DO I READ A JUNOS CONFIG?

March 22, 2020 Chris 2

In this first part of my new series, I explain why a Junos config looks the way it does. What’s wth the curly brackets and the spacing? Click to find out!

NEW SERIES: A GUIDE TO JUNOS, FOR IOS ENGINEERS
junos junos for ios engineers 

NEW SERIES: A GUIDE TO JUNOS, FOR IOS ENGINEERS

March 12, 2020 Chris 4

Are you an IOS engineer? Are you confused as heck about how Junos works? Then you’ve come to the right place. Welcome to this introductory post on Junos For IOS Engineers!

MULTICAST: IGMP VERISON 3 ON JUNIPER ROUTERS (FOR JNCIP & JNCIE STUDENTS)
juniper junos multicast routing 

MULTICAST: IGMP VERISON 3 ON JUNIPER ROUTERS (FOR JNCIP & JNCIE STUDENTS)

March 7, 2020 Chris 0

Today we’re looking at what advantages IGMPv3 brings to the table! Give this a read to see packet captures and full config for the whole topology.

JNCIP-ENT: THE ULTIMATE RESOURCE FOR JUNIPER’S PROFESSIONAL ENTERPRISE CERT
juniper junos 

JNCIP-ENT: THE ULTIMATE RESOURCE FOR JUNIPER’S PROFESSIONAL ENTERPRISE CERT

January 19, 2020 Chris 10

If you’re thinking about taking Juniper’s excellent Professional Enterprise exam, give this post a read – I’ve hooked you up with a ton of useful links to help you to succeed!

MULTICAST: IGMP ON JUNIPER ROUTERS, FOR JNCIP & JNCIE STUDENTS
juniper junos multicast 

MULTICAST: IGMP ON JUNIPER ROUTERS, FOR JNCIP & JNCIE STUDENTS

January 7, 2020 Chris 0

IGMP is a really simple protocol – but if you want to be an expert, you’ll want to know what’s happening at a packet level. That’s why in this post we have lots of fun with packet captures. If you’re studying for JNCIP or even JNCIE, you won’t want to miss this post!

A BEGINNER’S GUIDE TO MULTICAST, ON JUNIPER ROUTERS. PART 1: THE THEORY.
juniper junos multicast 

A BEGINNER’S GUIDE TO MULTICAST, ON JUNIPER ROUTERS. PART 1: THE THEORY.

December 16, 2019 Chris 6

This is the first in my new series of posts about multicast! In later posts we’ll focus on Junos configuration. But first, let’s get nice and comfortable with the theory. Click here to learn all about it!

MY JNCIE-SP EXAM EXPERIENCE
studying advice 

MY JNCIE-SP EXAM EXPERIENCE

December 2, 2019 Chris 14

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.

HOW TO STUDY NETWORK ENGINEERING, WITHOUT FEELING GUILTY FOR NOT STUDYING
studying advice 

HOW TO STUDY NETWORK ENGINEERING, WITHOUT FEELING GUILTY FOR NOT STUDYING

October 3, 2019 Chris 6

Oh boy, studying for networking can be overwhelming! There’s so much to learn, and so little time. If you feel that way, hopefully some of the tips in this post will help you to study smart, not hard.

HUB-AND-SPOKE MPLS L3VPNs – ADVANCED CUSTOMISATION, ON JUNIPER JUNOS ROUTERS
juniper junos mpls routing vpn 

HUB-AND-SPOKE MPLS L3VPNs – ADVANCED CUSTOMISATION, ON JUNIPER JUNOS ROUTERS

September 7, 2019 Chris 0

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!

HUB-AND-SPOKE MPLS L3VPNs WITH ONE INTERFACE, ON JUNIPER JUNOS ROUTERS
bgp juniper junos mpls vpn 

HUB-AND-SPOKE MPLS L3VPNs WITH ONE INTERFACE, ON JUNIPER JUNOS ROUTERS

August 30, 2019 Chris 0

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 MPLS L3VPNs WITH TWO INTERFACES, ON JUNIPER JUNOS ROUTERS
bgp juniper junos mpls vpn 

HUB-AND-SPOKE MPLS L3VPNs WITH TWO INTERFACES, ON JUNIPER JUNOS ROUTERS

August 24, 2019 Chris 0

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!

TERMINATING ACTIONS IN JUNOS ROUTING POLICY (Sample Chapter from Juniper’s Ambassadors Cookbook 2019)
bgp jncis juniper junos routing 

TERMINATING ACTIONS IN JUNOS ROUTING POLICY (Sample Chapter from Juniper’s Ambassadors Cookbook 2019)

August 18, 2019 Chris 2

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!

INTERPROVIDER OPTION C, ON JUNIPER JUNOS ROUTERS – PART 3: USING RSVP, AND PUTTING BGP-LU INTO INET.0
juniper junos mpls routing vpn 

INTERPROVIDER OPTION C, ON JUNIPER JUNOS ROUTERS – PART 3: USING RSVP, AND PUTTING BGP-LU INTO INET.0

July 10, 2019 Chris 2

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!

INTERPROVIDER OPTION C, ON JUNIPER JUNOS ROUTERS – PART 2: THE THREE LABEL STACK, AND THE USE CASE VS OPTION B
bgp juniper junos mpls routing vpn 

INTERPROVIDER OPTION C, ON JUNIPER JUNOS ROUTERS – PART 2: THE THREE LABEL STACK, AND THE USE CASE VS OPTION B

July 10, 2019 Chris 0

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)

INTERPROVIDER OPTION C, ON JUNIPER JUNOS ROUTERS – PART 1: CONFIGURATION WITH LDP (INCLUDES FULL TOPOLOGY CONFIG!) (JNCIP-SP, JNCIE-SP)
bgp juniper junos mpls routing vpn 

INTERPROVIDER OPTION C, ON JUNIPER JUNOS ROUTERS – PART 1: CONFIGURATION WITH LDP (INCLUDES FULL TOPOLOGY CONFIG!) (JNCIP-SP, JNCIE-SP)

July 10, 2019 Chris 2

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.

A QUIRK OF TRACEROUTE THAT YOU’LL WANT TO KNOW ABOUT
ipv6 routing troubleshooting 

A QUIRK OF TRACEROUTE THAT YOU’LL WANT TO KNOW ABOUT

June 27, 2019 Chris 6

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 ON JUNIPER ROUTERS (FOR JNCIE-SP STUDENTS)
bgp juniper junos mpls routing 

BGP LABELED-UNICAST ON JUNIPER ROUTERS (FOR JNCIE-SP STUDENTS)

May 29, 2019 Chris 22

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!

INTERPROVIDER OPTION B, ON JUNIPER JUNOS ROUTERS (INCLUDES FULL TOPOLOGY CONFIG!) (JNCIP-SP, JNCIE-SP)
bgp juniper junos mpls routing vpn 

INTERPROVIDER OPTION B, ON JUNIPER JUNOS ROUTERS (INCLUDES FULL TOPOLOGY CONFIG!) (JNCIP-SP, JNCIE-SP)

May 19, 2019 Chris 4

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!

INTERPROVIDER OPTION A, ON JUNIPER JUNOS ROUTERS (INCLUDES FULL TOPOLOGY CONFIG!) (JNCIP-SP, JNCIE-SP)
bgp isis juniper junos mpls vpn 

INTERPROVIDER OPTION A, ON JUNIPER JUNOS ROUTERS (INCLUDES FULL TOPOLOGY CONFIG!) (JNCIP-SP, JNCIE-SP)

May 12, 2019 Chris 6

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”.

MPLS VPNs AND JUNOS ROUTING POLICY: LESSONS IN TROUBLESHOOTING JUNIPER ROUTERS
bgp jncis juniper junos routing troubleshooting 

MPLS VPNs AND JUNOS ROUTING POLICY: LESSONS IN TROUBLESHOOTING JUNIPER ROUTERS

January 4, 2019 Chris 2

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!

JUNOS ROUTING POLICY, BGP COMMUNITIES, AND MPLS VPNs
bgp jncis juniper junos mpls routing troubleshooting 

JUNOS ROUTING POLICY, BGP COMMUNITIES, AND MPLS VPNs

January 4, 2019 Chris 0

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!

JNCIA-CLOUD: THE ULTIMATE RESOURCE FOR JUNIPER’S SDN CERTIFICATION
cloud contrail jncia juniper routing sdn 

JNCIA-CLOUD: THE ULTIMATE RESOURCE FOR JUNIPER’S SDN CERTIFICATION

November 26, 2018 Chris 25

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

JNCIP-SP: THE ULTIMATE RESOURCE FOR JUNIPER’S PROFESSIONAL SERVICE PROVIDER CERT
juniper junos 

JNCIP-SP: THE ULTIMATE RESOURCE FOR JUNIPER’S PROFESSIONAL SERVICE PROVIDER CERT

November 12, 2018 Chris 6

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!

LESSONS IN JUNOS TROUBLESHOOTING: FIXING A LAN WITH A WEIRD PROBLEM
juniper junos troubleshooting 

LESSONS IN JUNOS TROUBLESHOOTING: FIXING A LAN WITH A WEIRD PROBLEM

October 14, 2018 Chris 0

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.

MOVING LSPs BETWEEN INET.3 and INET.0 ON A JUNIPER ROUTER
bgp jncis juniper junos mpls routing 

MOVING LSPs BETWEEN INET.3 and INET.0 ON A JUNIPER ROUTER

October 8, 2018 Chris 5

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.

JUNOS ROUTERS: WHAT DOES THE INET.3 TABLE ACTUALLY DO?
bgp jncis juniper junos mpls routing 

JUNOS ROUTERS: WHAT DOES THE INET.3 TABLE ACTUALLY DO?

October 8, 2018 Chris 19

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?

JUNOS RPM: TESTING YOUR JUNIPER NETWORK WITH REAL-TIME PERFORMANCE MONITORS
jncis juniper junos 

JUNOS RPM: TESTING YOUR JUNIPER NETWORK WITH REAL-TIME PERFORMANCE MONITORS

August 15, 2018 Chris 2

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.

USING WILDCARD MASKS TO FILTER ODD OR EVEN NUMBERED IP ADDRESSES: JUNIPER JUNOS & CISCO IOS
junos routing subnetting troubleshooting 

USING WILDCARD MASKS TO FILTER ODD OR EVEN NUMBERED IP ADDRESSES: JUNIPER JUNOS & CISCO IOS

July 16, 2018 Chris 5

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.

Junos: IS-IS Study Notes, Part 3 – Interfaces, Metrics, the DIS, and Pseudonodes
isis jncia jncis juniper junos routing troubleshooting 

Junos: IS-IS Study Notes, Part 3 – Interfaces, Metrics, the DIS, and Pseudonodes

July 6, 2018 Chris 4

It’s the third part in our series on IS-IS! In this post you’re going to learn about interface types, broadcast interfaces, metrics, and the OSPF equivalent of the designated router – the “designated intermediate system”, or DIS. It’s way more efficient than how OSPF does it. I think you’re gonna enjoy this one!

Junos: IS-IS Study Notes, Part 2 – LSPs and Message Types
isis jncia jncis juniper junos routing 

Junos: IS-IS Study Notes, Part 2 – LSPs and Message Types

July 6, 2018 Chris 4

In Part 2 of my ongoing series on IS-IS, we take a look at some real nice packet captures. You’re going to learn how hello and LSP messages work, how adjacencies work, and we even explore our feelings together, so that we can finally find inner-peace with ourselves. Great!!!

Junos: IS-IS Study Notes, Part 1 – For Juniper’s JNCIS-SP and JNCIS-ENT Exams
isis jncia jncis juniper junos routing 

Junos: IS-IS Study Notes, Part 1 – For Juniper’s JNCIS-SP and JNCIS-ENT Exams

July 6, 2018 Chris 8

Here’s the first post in my five-part guide to IS-IS. Wow, what a Christmas treat! In this first post we compare IS-IS to OSPF; we’ll talk about Level 1 and Level 2; we’ll explain the unique 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.

JUNOS: AGGREGATE ROUTES VS GENERATE ROUTES – HOW TO SUMMARISE ON JUNIPER ROUTERS
juniper junos routing subnetting 

JUNOS: AGGREGATE ROUTES VS GENERATE ROUTES – HOW TO SUMMARISE ON JUNIPER ROUTERS

March 25, 2018 Chris 15

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!

JUNOS: CHASSIS CLUSTERS – A BEGINNERS GUIDE TO JUNIPER SRX HIGH AVAILABILITY
high availability juniper junos routing 

JUNOS: CHASSIS CLUSTERS – A BEGINNERS GUIDE TO JUNIPER SRX HIGH AVAILABILITY

March 3, 2018 Chris 21

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.

OSPFv3 – HOW TO READ IPv6’s OSPF DATABASE
ipv6 ospf ospfv3 routing 

OSPFv3 – HOW TO READ IPv6’s OSPF DATABASE

January 5, 2018 Chris 3

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.

OSPFv3: THE NEW LSA TYPES IN IPv6 OSPF
ipv6 ospf ospfv3 routing 

OSPFv3: THE NEW LSA TYPES IN IPv6 OSPF

January 5, 2018 Chris 0

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!

OSPF: STUB AREAS VS STUB NETWORKS: WHAT IS THE DIFFERENCE?
ospf routing 

OSPF: STUB AREAS VS STUB NETWORKS: WHAT IS THE DIFFERENCE?

December 6, 2017 Chris 0

Big-ups to the designers of OSPF for giving very similar names to two totally different things. In this post, we clarify the difference between stub areas and stub networks.

OSPF: WHAT IS A STUB NETWORK?
ospf routing 

OSPF: WHAT IS A STUB NETWORK?

December 6, 2017 Chris 5

When you’re first getting to grips with your router’s OSPF database, you might see mention of something called a “stub network”. And let me tell you: never before have I seen a phrase so clumsily defined. Let’s take a look, and find out what a stub network actually is.

OSPF: WHAT IS A STUB AREA?
junos ospf routing 

OSPF: WHAT IS A STUB AREA?

December 6, 2017 Chris 7

Stub areas are a very easy concept to understand, but it comes with a ton of specific jargon that can make it super-daunting. So, in this post I’ll take time to explain these concepts, and to define just enough jargon to make you feel like you’re part of the elite. We’ll take it slow, like new lovers, or someone cooking an expensive turkey.

Routers and Firewalls: Stateless Rules vs Stateful Rules
security 

Routers and Firewalls: Stateless Rules vs Stateful Rules

September 25, 2017 Chris 0

Do you know the difference between a stateful rule and a stateless rule? No? Well, you’d better click this post then!

Put Your Firewall Rules In The Correct Order
security 

Put Your Firewall Rules In The Correct Order

September 25, 2017 Chris 0

If you’re brand new to creating access lists, firewall rules, or security policies, you might wonder how the order of your rules can make a difference. In fact, they can make a BIG difference! This post shows you exactly why – and how to potentially avoid an outage.

Hi there!

Welcome to my blog of networking and nonsense.

I’m Chris. By day I’m a London-based network engineer, instructor, and courseware developer for Juniper Networks. But in my spare time I come here to write some sweet sweet blog posts to help you with your networking studies, with just as much focus on fun as on the tech. I hope you like what you see!

In this corner of the information super-highway you’ll find tons of stuff about BGP, MPLS, OSPF and IS-IS. If that sounds fun then you’ve come to the right place. You’ll also find posts I made on my journey towards JNCIE-SP, which I hope will help you on your own journey.

There’s a big focus on Juniper and Junos in this blog, but tons of the theory is entirely vendor-neutral. No matter what networking platform you’re more comfortable with, you’re very welcome here.

Please note that it costs £750,000 to read my posts. This is enshrined in international law, and late payment will result in the fee being scrapped and replaced with a £25 fine. I did ask the United Nations to scrap this law entirely, but they insisted that it stayed. Sorry readers, it’s out of my control.

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