Archives for January 2015

An Overview of inSSIDer

January 27, 2015 by Rowell Dionicio Leave a Comment

If you are in need of planning or troubleshooting wifi but you’re on a budget, then inSSIDer by Metageek may be a good start for you. inSSIDer is a tool used to show you what your wireless environment looks like.

inSSIDer comes in two version, inSSIDer and inSSIDer Office.

inSSIDer

$19.99
Uses built-in wifi
For Windows and Mac

inSSIDer for Office

$199.99
Includes Wi-Spy Mini
Assists in troubleshooting interference

Radios and ESSIDs

When you open inSSIDer, and depending on whether you organized the main pane via Radio or ESSID, you will be presented with a list. When organized by Radio you get a number of columns:

Radio’s MAC address
Broadcasted SSID
What channel the SSID is on
Signal strength (in dBm)
Protocol
Security
Data rates

Selecting Radio is great if there is usually one access point. If you see two channels listed under the Channel column, e.x. 36+40, it means that wireless network is channel bonding to utilize two 20 MHz channels to form a single 40 MHz channel for increased bandwidth.

Select ESSID and the list of wireless networks will be organized by the SSID name. This is useful if there are multiple access points broadcasting the same SSID. You get the same columns but in addition there is a BSSID count which will tell you how many radios are seen for a particular SSID.

On the first column, under Radio or ESSID, you may see a chain link icon. That shows what SSID your laptop is associated with. [Read more…] about An Overview of inSSIDer

Windows Server NLB VIP Multicast Mode Through Cisco Switch

January 19, 2015 by Rowell Dionicio 5 Comments

If you are unable to connect to a Windows Server Network Load Balancing (NLB) Virtual IP address configured for Multicast Mode it is because of the way your Cisco switch interacts with Microsoft NLB.

Symptoms

Cannot connect to Windows Server NLB Virtual IP address
Cannot ping Windows Server NLB Virtual IP address
Microsoft NLB Multicast Mode not working

I won’t go into the details of how NLB works but in short, client requests are distributed across different servers. To configure NLB, you can use three modes:

Unicast
Multicast
IGMP

Using Multicast Mode

When using Multicast mode, the cluster members will respond to ARPs using their virtual IP address and a multicast MAC address. Without the proper configuration on the switch you will not be able to connect to the Virtual IP address.

This will not work because within the ARP request packet is a unicast IP address and a multicast MAC address. Troubleshooting it can be frustrating but a Cisco switch will ignore this. Below is the configuration to be done on the switch.

Cisco Switch Configuration

To resolve the problem, create a static ARP entry for the Virtual IP Address to the NLB MAC address. Then create a static MAC address entry to the VLAN and interfaces used by the cluster.

In my case, my virtual IP address is 192.168.10.10 with MAC address of 03bf.0a65.05fa. That IP address is on VLAN 10 and the servers’ interfaces are part of a port-channel, both Port-Channel1 and Port-Channel2.

The following configuration is as follows:

arp 192.168.10.10 03bf.0a65.05fa
mac address-table static 03bf.0a65.05fa vlan 10 interface Port-Channel1 Port-Channel2

Some configuration items to note.. not all Cisco switches will support a static entry of a MAC address to multiple interfaces. In my case I am using a Cisco Catalyst 4500-X in VSS mode. The servers had two network interfaces configured into an EtherChannel.

Wireless Design Resources

January 6, 2015 by Rowell Dionicio 1 Comment

I’m far from calling myself an expert in wireless but I know how to avoid the most common mistakes I see being made in different environments. Because wireless signal is invisible, some may think wireless is easy to deploy. Just pop up a few access points here and there and we’re good to go, right? I wish it were that easy but there’s more to it.

What I love about the wireless industry are the different individuals who are making waves (no pun intended) by giving back. These are engineers who live and breathe wireless and only want to see it improve.

Wireless Capacity Planner

Take Andrew von Nagy, author of Revolution Wifi, as an example. He published a Wireless Capacity Planner which I recommend to anyone who is deploying wireless. I commend his work and generosity to the industry. This tool is essential for explaining the Why in wireless. Included in the planner is an Excel sheet in which you can specify what kind of APs will be deployed and what kind of clients will be using wireless and in the end it will calculate approximately how many radios you should use.

It’s obviously a better planning utility than just guessing at which AP to use, how many, etc. Not only do you get the Excel sheet but Andrew also includes a PDF going into wireless capacity planning.

Designing For Capacity

Andrew doesn’t stop there. He has produced exceptional material. One example is his presentation on Designing for Capacity. One of his slides mentions the typical design process which focuses mostly on signal strength and coverage.

Download his presentation and soak in the education.

Education

Revolution Wifi has been a big influence in my career, regarding wireless. I have learned so much from his perspective. One thing I did come to ends with is that the CWNA is highly beneficial to anyone in the wireless industry.

I am currently in my early stages of studying for the CWNA but I have read through the book front to back. It is a lot to take in but very interesting to me. The book is a great place to start if you are just getting started in wireless.