Active WiFi Site Survey Using Meraki and WLANPi

I recently had to do some on-site active Wi-Fi testing using a Meraki MR33 access point. I grabbed my WiFiSurveyKit and threw an MR33, an 11’ iPad Pro and my Ekahau Sidekick in there to get the job done.

When I arrived at the site, setup was quick and easy. I flipped open my case, got out the AP and connected it to the AccelTex Accelerator battery POE port.

Unfortunately, I had forgotten one thing about Meraki access points: they need to be set in survey mode or connected to a DHCP source to get online and broadcast an SSID. With no access to an Internet-connected network to configure the AP, this posed an issue. The units are supposed to automatically broadcast an SSID that says “meraki-scanning” but mine didn’t.

Configuring the WLANPi

Luckily, the WLANPi is part of the standard Wi-Fi survey kit. I connected the USB power cord to the USB port on the WiFiSurveyKit and the Ethernet port to the LAN connection on the AccelTex Accelerator battery thinking that would kick out a DHCP lease and get the AP online to at least to give me a bad-gateway or scanning ssid, but that didn’t work either … probably because the WLANPi doesn’t kick out DHCP on the Ethernet interface I learned. So, wat do now?

Configuring DHCP on the WLANPi for a USB Ethernet adapter

Good thing I had a USB Ethernet adapter! I plugged it into one of the USB ports on the WLANPi and connected a patch cable from the USB Ethernet adapter to the LAN port on the AccelTex Accelerator. I plugged the main Ethernet port on the WLANPi into the Ethernet port on my laptop, started up DHCP Services, got an IP on the WLANPi, SSL’d to it and began my hunt for DHCP config files.

Now, you can just assign an IP to your interface if you don’t have a DHCP server, but you should totally have a DHCP server on your device, just sayin.

Now for the next part, I’ll just skip on over to the part where I configured it:

  • First, you need to edit the DHCP server and tell it to push DHCP on the eth1 interface that will be created when you plug in the USB Ethernet adapter.
    (Note: it’s not a USB interface, the WLANPi recognizes the adapter and creates an eth port for it)

sudo edit /etc/default/isc-dhcp-server

Add eth1 to the bottom of the config file in the INTERFACESv4 section:

INTERFACESv4="usb0" should be changed to INTERFACESv4="usb0 eth1"

  • Next you need to add a static IP to the USB Ethernet Adapter. Make sure this is the same IP address you define as the gateway address in the DHCP scope!

sudo edit /etc/network/interfaces

Add a static IP for eth1 by adding this to the /etc/network/interfaces

iface eth1 inet static
 address 172.16.100.1 
 netmask 255.255.255.0
 gateway  172.16.100.1  

Edit /etc/dhcp.config

  • Now you need to create a new DHCP pool for devices connected to eth1 in the same network as the eth1 interface 172.16.100.0. This config will give you 150 leases in your DHCP pool with a lease time of 1 hour.

    Edit the DHCP config:
    sudo edit /etc/dhcp.config

    and add this to the /etc/dhcp.config file:
subnet 172.16.100.0 netmask 255.255.255.0 {
     range 172.16.100.100 172.16.100.250;
     default-lease-time 3600;
     max-lease-time 7200;
     option subnet-mask 255.255.255.0;
     option routers  172.16.100.1;
     option domain-name-servers 8.8.8.8; 
} 

Reboot. Success.

Something important for Meraki users to know

There was something important I learned through this: the Meraki AP has to have a gateway IP provided by DHCP and it has to be able to hit that IP defined as the gateway from the DHCP lease or else it won’t come come online.

How do I know this?

A few ways:

1. I didn’t think a gateway address was necessary, so I didn’t define one in my initial DHCP scope

2. After thinking that maybe it requires one, I added a default gateway of 172.16.100.1.

3. However, when I originally set up the IP address on the eth1 interface it was 172.16.100.20 and when I changed it to .1 it all came online.

Getting it all up and running

Once I had all of this as a working config, I was able to plug the AP into the WiFiSurveyKit Ethernet port, the WLANPi into the USB port to power it and I was rocking and rolling! I probably could’ve use the Ethernet port built in to the WLANPi, however I had an external USB Ethernet adapter with me and that allowed me to set it up in a way that I can reuse this if I ever need to without messing anything else up.

It took a little bit of effort to get this done, but with the right tools in a little bit of knowledge of linux, it got the job done! If you need help, drop a comment or @ me on twitter @wirelessnerd!

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