interference

CTS 054: 4 Scary Things Lurking in Your Wi-Fi

In the spirit of Halloween I wanted to go into a theme of scare and fright. While these may not make the hair on your neck stand, I don’t know maybe they do, these issues can lead to managing a scary wireless network. Scary because of end user complaints and because these can be running on newer wireless networks.

Those four scary things are

  1. Low data rate clients
  2. WPA2, even WEP
  3. 2.4 GHz Zombies
  4. Non Wi-Fi Interference

But before we jump into those 4 things, I wanted to update everyone on my journey to CWNE. This weekend I decided to take the CWDP exam. After a little under a month of studying I successfully passed.

The biggest resource I used was the official study guide by Tom Carpenter. It covered all the objectives of the exam. I felt this one was easier for me than the CWNA or CWAP. The topics were straight forward and common sense. This is probably because of my experience coming from designing some wireless networks but it came natural for me.

Now I plan on tackling the CWSP. Probably my weakest area but I look forward to learning from the Sybex book that was released in September 2016. I also plan on doing quite a few labs to get the security topics down.

4 Scary Things Lurking In Your Wi-Fi

Low data rate clients

Low data rate clients take longer to communicate over the air. They slow down devices trying to communicate on faster data rates. This makes it an inefficient wireless network.

An easy solution is to disable lower data rates such as 1, 2, 5.5, 6, and even 9 Mbps.

Keep in mind that this will shrink your cell size. So design properly!

WPA2, even WEP

I’ve seen some networks still utilizing WEP. There’s no use for this anymore. It’s been proven to be insecure and newer devices support much stronger encryption. WPA2 is also now crackable so it’s time to use stronger security.

Both security methods are a management nightmare because a passphrase has to be changed on every device.

The best solution here is to use RADIUS as much as possible. Keep WPA2 only devices on a separate SSID.

2.4 GHz zombies

The IoT band. The land of interference. A place where all single band clients get together. 2.4 GHz is a crowded spectrum.

Move your clients to 5 GHz as much as possible to avoid the congestion seen on 2.4 GHz. To troubleshoot issues on 2.4 spectrum use a protocol and spectrum analyzer.

Non Wi-Fi Interference

This also relates to the previous item. Non Wi-Fi interference causes high retransmissions on the network. This leads to low throughput.

End users characterize this as slow Wi-Fi, unusable, and poor performance.

Start looking into causes of anything over 15% retry rate. You can use tools such as Wireshark or Metageek’s Eye P.A.

Check out this previous episode around Spectrum Analysis while you’re at it.

CTS 048: Cisco Mobility Express

Cisco Mobility Express

Cisco Mobility Express is a small to medium sized Wi-Fi solution which can be deployed in just under 20 minutes. In this episode, I talk about my what Cisco Mobility Express entails and how I configured a couple of Cisco 1800 series access points.

Other access points that can be controllers with Cisco Mobility Express include the 2800 and 3800 series access points. This is a special image and not the lightweight images we typically use with the larger controller based models. What’s so special with Cisco Mobility Express is there is a built-in controller. This AP can serve wireless clients and function as a controller to manage up to 25 access points and 500 clients.

Installation

Deploying a Cisco Mobility Express controller can be completed in under 20 minutes. After completing the boot up process, a new SSID, CiscoAirProvision, will be enabled. It can be joined using your desktop/laptop computer or with an app, CiscoWireless.

For testing purposes I used the app on my iPhone which was surprisingly simple.

It’s only 5 steps:

  1. Configure an admin account
  2. Setup the controller – System name, management IP address, etc.
  3. Configure wireless networks
  4. Set up RF Parameter Optimization
  5. Confirm and Reboot

Reminder: Configure your switch port properly! If you’re tagging multiple VLANs for your wireless networks, be sure to configure trunk ports to the access point.

A controller can function as one single controller but for redundancy, each Cisco Mobility Express AP (1800,2800,3800 series) can be redundant to each other. But if you want to statically configure a primary and secondary controller, you can do so using the CLI.

The election of a controller happens in one of three ways:

  • User defined
  • Least client load
  • Lowest MAC address

All of your advanced troubleshooting will be done using the CLI as well.

Within the web interface, to manage the controller, you have the ability to modify the configuration such as radio policies for your SSID, VLAN tags for an SSID and advanced settings such as channels, channel widths, and transmit power.

Monitoring will yield statistics on access points and individual wireless clients.

You can view access point statistics such as:

  • Channel utilization
  • Interference
  • Configured data rates
  • Throughput
  • Noise
  • Current transmit power

Client statistics collected include:

  • MAC address
  • Uptime
  • Current SSID connected to
  • Signal strength
  • Basic client capabilities

In addition to the statistics above, you can view the top applications used by each client and on the network.

Useful Commands

To get to ap level from controller:

apciscoshell

To get back to controller cli from ap cisco shell:

AP>logout

Troubleshooting AP join issues from controller:

debug capwap events enable

More detail:

debug capwap detail enable

View errors:

debug capwap errors enable

What you can configure via the AP:

Set static IP address:

capwap ap ip <ip-address> <subnet mask> <default-gateway>

Configure static controller IP:

capwap ap primary-base <controller-name> <ip-address>

Setup a primary and secondary AP for controller:

config ap priority 4 <ap>

config ap priority 3 <ap>

Links and Resources

15 Wi-Fi Blogs To Read via Network Computing

Are there any other blogs missing from this list? One I can think of is http://www.mikealbano.com/

Interference sources on the Wi-Fi Network via Netscout

Cisco to dismiss up to 5500 employees or 7% of their workforce via Arstechnica

How To Deploy Cisco Mobility Express via Packet6

Troubleshoot AP Joining Issues via Packet6

Cisco Mobility Express Deployment Guide via Cisco