A QUIRK OF TRACEROUTE THAT YOU’LL WANT TO KNOW ABOUT
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!
Read more
troubleshooting
MPLS VPNs AND JUNOS ROUTING POLICY: LESSONS IN TROUBLESHOOTING JUNIPER ROUTERS
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!
Read more
JUNOS ROUTING POLICY, BGP COMMUNITIES, AND MPLS VPNs
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!
Read more
LESSONS IN JUNOS TROUBLESHOOTING: FIXING A LAN WITH A WEIRD PROBLEM
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.
Read more
USING WILDCARD MASKS TO FILTER ODD OR EVEN NUMBERED IP ADDRESSES: JUNIPER JUNOS & CISCO IOS
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.
Read more
JUNOS: IS-IS STUDY NOTES, PART 3 – FOR JUNIPER’S JNCIS-SP and JNCIS-ENT EXAMS
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!
Read more
TROUBLESHOOTING: USING THE DEBUG CONDITION INTERFACE COMMAND
There’s two handy Cisco troubleshooting tips I’ve learnt during my time as a network engineer. The first is to just ignore a problem and go to the pub. The other tip is the debug condition command, which helps you to troubleshoot by limiting debug messages to certain interfaces, IP addresses, MAC addresses, and a whole lot more.
Read more
EIGRP: TROUBLESHOOT AUTHENTICATION USING THE SHOW KEY CHAIN COMMAND
A little while ago, I was mucking about with some EIGRP authentication in a lab. Because when I party, I party hard. Rock and roll is an integral part of my soul. Anyway, EIGRP was running. Neighbors were formed. And then I added a keychain, and applied it to my interfaces. The neighborship dropped, tried to re-establish – and failed. Why? Let’s find out!
Read more