Runner or Sprinter?
Alright, the name of the show is “No Strings Attached” because well we are wireless so we don’t need strings right? Sort of, we do need at least 1 “string” and that is the one connected to our access point. While we have focused a lot on the tools needed to test and troubleshoot wireless today we are going to focus on that string, the wired connection from our AP to switch. There are two “go to” devices that I carry in my bag whenever I’m doing a turn-up or troubleshooting activity at customer sites. One of them I carry pretty much all the time because it’s so small and lightweight, that is the LinkSprinter from NETSCOUT. We did a video on the LinkSprinter when it first came out so please click this link here to check it out.
Why do we love this little device? Well it’s extremely small and portable, checks PoE, provides hotspot connectivity to mobile device for status, and uploads to the Link-Live.com cloud service. There are 3 models of the LinkSprinter available: 100, 200, and 300. The main difference between the 100 & 200 is that the 200 provides that hotspot connectivity to a mobile device for real time results. The 300 adds the ability to do a simple cable fault check and can show the distance to open or short. All of the models support verifying PoE on the port, link status to the port, DHCP, CDP/LLDP information from port, and finally pinging a host that is configureable. I personally go with the 200 typically for around $300 because I’m not overly concerned with where the fault is, I just want to know if it’s working or not. If it isn’t working I’ll generally get in touch with the low voltage crew that did the work to have them test further and fix. If I ran the cable then I usually will have verified the cable with my purpose built cable testing tool. The main feature to get is the hotspot abilities to see the results from your mobile device. Connecting your phone or tablet to the hotspot allows you to see in real time the results, adjust the “Internet Test” from either TCP port connection or basic ping to a host, and configure the wireless SSID/channel. My workflow if I’m installing a new AP usually consists of plugging in the LinkSprinter, getting the test result, and replying with a cable number so that the Link-Live database is updated. This quick verification helps me ensure that the cable is connected and to the right port on the correct VLAN. I can then run a report from Link-Live after deployment certifying the installation essentially. There are a few things I would love to see added to this, such as the ability to send a custom VCI string to the DHCP server so I could emulate an AP requesting the IP address of the Cisco WLC for example, but all things considered this is a great device. Adding the ability to create customized DHCP request options would allow this device to be even more flexible and provide another layer of quick testing that doesn’t require you to break out a packet capture device. What if you want more advanced information though regarding your port you are connected to? That’s where the LinkRunner series comes into play.
Those of you that are familiar with the AirCheck from NETSCOUT will quickly recognize the form factor of the LinkRunner AT. This is the same classic yellow rubberized unit that can withstand a drop from heights and keep on running. You’ll quickly notice there are 2 RJ45 jacks and a SFP slot on the unit to perform the various tests. Upon turning on the unit you are presented with a basic 4 option home screen: Switch, Cable, AutoTest, and Tools. Most of your time will be spent in Switch if you are just checking a port. Once you connect a live ethernet cable or fiber to the top ports the LRAT will display as much information as it can about the port you are connected to. For example if your switch will give its name you’ll get that as well as the model. It’ll also inform you about the switch IP address and the port that you are plugged into. Then a graphic will tell you 10/100/1000 and duplex along with the VLAN. This quick glance check lets you see what’s going on, but does open up a potential concern given that it does tell you the switch name and IP of the switch, an attacker could use this device to determine what management IP to try to brute force, but we aren’t here to talk about that! From here my next check would be to go back to the home screen and select AutoTest. AutoTest will run through as series of checks: Switch Port, IPv4/IPv6, Gateway ping, DNS 1 ping, DNS 2 ping, and finally will attempt to send the data to Link-Live if configured. The Link section tells me about the Rx pairs and polarity, switch port again informs me of the previously mentioned data, IPv4 section lets me know about my DHCP information received from the VLAN the port is configured for, and finally I have the ping times for the targets that I can configure under Tools. Ok so you probably read through this first paragraph and are sitting there thinking to yourself this doesn’t really seem to give me any advanced data that the LinkSprinter gives me, that’s not the case. Let’s take a look at the Tools section to see all the advanced parameters we can configure and where the power of the LRAT shines.
Under tools you’ll see a ton of menu options that you can get into. Some of them are the obvious ones (IP Configuration and VLAN), some maybe not. I mentioned we could customize the ping targets, that is done under the AutoTest configuration and we can add up to 10 targets. But this isn’t necessarily just a basic ping, we are checking ports again so we can verify if we can get to a specific port and see if a firewall for example is blocking us. One of my favorite features is the PoE configuration, yes the LinkSprinter checks if PoE is available but it doesn’t check load, that’s where the LRAT expands on the feature! You can specify which PoE Class you want to pull to ensure you can actually get the power you need and the switch has enough in its budget. Remember that concern I brought up earlier about getting switch information? What if you have a network deployed with 802.1X to block access until authorized? LRAT has you covered there as well. We can setup the LRAT with 802.1X credentials using the Windows only (I know, I wish there was an OS X version!) management software which will let you install certificates or add usernames/password combinations for use in the authentication process.
For those that are doing physical cable testing and troubleshooting the LRAT provides quite a bit of features for that as well. Couple the LRAT with a tone device like the Intellitone and you can identify wires throughout the runs or at the closet. I personally don’t have an Intellitone at the moment but will be picking one up for those just in case times when I need to do this. There is also a component called a WireView Cable Identifier, the LRAT 2000 comes with #1 and #2-6 are available for purchase separately. These allow you to terminate an ethernet cable into the numbered adapters and then check the cable as well as identify the cable from the LRAT screen. This comes in handy for when your cable map doesn’t exactly match what was installed or patched (never happens right?). Finally the LRAT unit can be used as a standard cable tester to look for mis-wired, open pairs, and identify the distance of the cable or where the short is.
I’ve been using the LinkSprinter since they were first available and it is a go to device for sure. The other week while working with Keith Parson’s he mentioned another use case that isn’t even a “feature” if you will of the device. If you have the 200/300 with hotspot capabilities you can turn on the hotspot, then use an AirCheck or other wireless utility to determine the dB loss of a wall or obstacle. I use the LinkSprinter around the house and at in-laws when troubleshooting issues, couple with the Link-Live service and you should never leave home without one. The LRAT unit has been great not only for testing switch ports and cables but also as a quick configurable device to do 802.1X testing and trunk port testing while leaving my laptop online viewing ISE/ClearPass logs and such. Both devices are near instant on which is great for conserving battery by not having to leave something on while you walk between test locations.
The only problem with all of these devices is just that, there are a lot of single use devices that we need to carry in our bags! I would love to see a device from NETSCOUT that allowed me to plug in licensable modules that enable AirCheck features or LRAT features by changing the top “section” of the device. Very rare am I needing to use both the AirCheck and LRAT at the same time, it’s a workflow device going from Step 1 to 2 to 3 in a non-parallel way. The Link-Live service is great and allows me to get data off of the devices without using Windows but for 802.1X profile management I do need to fire up my bootcamp partition which causes a little delay in my workflow. Key for me there is to make sure I’m prepped with an appropriate profile prior to going on site.
Ultimately I think both the LinkSprinter and LRAT (mainly the 2000) are must have devices for wired and wireless engineers. You can’t beat the durability, reliability, and ease of use both devices give you. While the cost of an LRAT 2000 is up there, the time saved on your projects should offset that cost in no time.
Disclosure of Material Connection: I received one or more of the products or services mentioned above for free in the hope that I would mention it on my blog. Regardless, I only recommend products or services I use personally and believe will be good for my readers. I am disclosing this in accordance with the Federal Trade Commission’s 16 CFR, Part 255: “Guides Concerning the Use of Endorsements and Testimonials in Advertising.”