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.
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.
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)
Last week I updated the core switches at one of our sites to two new fancy HP 5406zl. Along with all the nice new features that came with these two beasts was PoE on all ports. All was good and well, until today, when the logs on one of the switches started filling up with 3 errors about PoE delivery on a specific port.
After a lot of cable-tugging and google, it turned out that a subcontractor had installed a small V1810-8G switch in the network. And among other things, these small buggers can be fed by PoE on Port 1. But since it was hooked up with a wall-wart, that collided with the PoE-feed. One would think that HP could put in a bit of error checking on the PoE side so that a device that already have a functioning power supply does not request a PoE-feed.
So, if you’re struggling with a log full of PoE errors (I got 110 000 events in half a week), do a quick google if the connected device supports PoE.