The World’s Longest Console Cable – Smartflex Router Series


As everybody knows, console cables and their corresponding interfaces are a scourge on a network administrators existence. They are always too short, COM-ports get renumbered, Baud-rates are unknown, etc. By their very nature, you also have to be physically present in the vicinity of the box you’re trying to configure. Today we’re going to change all that, by constructing a wireless console cable adaptor with almost infinite range.

I can almost here people shouting something about SSH and Telnet to their screens, as well as something about the Airconsole. First and foremost, telnet and SSH are both wonderful, after you’ve configured the device, but for initial setup, they sadly can’t be used. Airconsole is quite nice, and I use it almost daily, but it’s useful when you want to sit somewhere comfortable when configuring a device in the same room as you, not so much when you want to be comfortable on a beach half a world away from the offending device.

This we’re going to change today, with one device, the B+B SmartFlex router.

Continue reading


How to Stack HPE/Aruba 2920 Switches – HP Networking Series Part 4


The 2920 series switches from HPE/Aruba has a special feature that no other switches in the old ProCurve/E-Series line-up has; dedicated stacking interfaces. On other HPE switches, stacking merely facilitates “simplified” management, by allowing you to manage any switch in the stack from the stack commander’s CLI. On the 2920 series however, you can use dedicated stacking interfacing, giving you 2 20 Gbps links to other switches in the stack and merging two to four switches into one coherent switch. This is quite similar on how stacking works on some Cisco models, but the specialized stacking interfaces gives you higher speeds between the members. In this article, I’ll show you have to set up the commander switch and how to add switches to the stack once it’s created. I’ll also go into how it affects the configuration of the switches, which is quite crucial if you want to stack switches that are already in production.

Continue reading

Setting up NTP on Cisco Switches – Cisco Networking Series Part 1


This is more for my own reference than anything else, but what follows here is a short tutorial on how to get NTP up and running on your Cisco iOS device.

First we need to get DNS working for the switch to be able to resolve the DNS name for the time server. If you run your own time server you can use the static IP for the NTP server and skip this step, but if you use one of the public NTP pools just resolving the domain name for the pool one time and hard coding that into your switch won’t do it. First of all, that NTP server might go down some time down the line, and then your time synchronization stops working. Secondly, and this is actually a far bigger problem, if you resolve the IP of a NTP pool, you’re actually only using one server in that pool constantly since the pools load balancing is constructed using DNS round robin. This skews the load on the (already heavily loaded) public NTP infrastructure, which isn’t very good. While we’re on the topic, if you are using public NTP servers, consider setting up your own internal NTP servers and have your clients sync to them, thus limiting the load you put on public NTP servers. If you, like me, run your own GPS NTP servers, then you can do as you like (but the DNS round robin trick is also useful to do internal load balancing and fail-over)

Continue reading

Peculiar Network Problem

This Monday I was called out to fix a computer that couldn’t get on-line. I quickly discovered that the problem wasn’t with the computer itself, but with it’s wired connection. The computer was wired as follows;

Control Room: Computer <-> Jack (unlabeled)

Electrical Room: Jack <-> Jack A1

Switch Room in another building: Jack A1 <-> Port 13 on the main switch

As you can see, it wasn’t very clear what was going on as the first connection wasn’t labeled. Also, the port number on the switch wasn’t that nice either.

Well, I started looking for clues. The weird thing was that both the switch and the computers port lights were on, so the connection was obviously good. Therefore I assumed that the NIC was faulty in the computer, and took the computer to my office to troubleshoot it. This turned out to be the exactly opposite to what I should have done, but more on that later.

So, I took the computer back to my office, and guess what? It worked perfectly. So now I didn’t really know what to think, but anyhow I needed to return it, so I went back there.

This time I checked every connection, and the all matched up, everything seemed to be working properly, but it didn’t. Then I noticed the give-away sign. The activity LED for port 13 was blinking like crazy. Like it was working at max capacity, which I knew that it didn’t since the computer didn’t send or receive any packages. So I figured that the switch might be faulty, and since half of it’s ports was unoccupied, I swapped the cable over to the next empty port, Port 15.

Then the weirdest thing happened. The LED for Port 15 went on, but the LED for Port 13 didn’t go out, it just kept going, blinking like crazy. Later I learned that there had been some tunderstorms in the area during the weekend, which had nocked out the climate control as well. The switched later failed compleatly on Tuesday morning, so I guess a voltage-spike must have fried it.