Archive for February 2011
Last week I went ahead and took the CWTS (Certified Wireless Technical Specialist) exam from the CWNP group, now I know they consider this almost a “sales” certification but I wanted to start with this exam just to see how the CWNP group present their exams compared to Cisco, Microsoft, RIM, and CompTIA. Well I managed to pass the exam with a 90% (70% is the minimum score required to pass) so I did fairly well on the exam. I did think a few of the questions were not worded in the best way, but it appears I understood what they were asking for.
My primary sources of study was the Official CWTS study guide from CWNP, along with their practice exams hosted off the CWNP website, not to mention a few years of supporting multiple wireless networks. Now I’m not usually one to say “yea get the official study guide you’ll be ok with that” but in this situation I have to recommend the official study guide. It does an amazing job at covering the CWTS exam objectives. Plus I found it a very easy book to read there plenty of clear concise explanations with enough images that promote the text (Images also span between some of major WLAN equipment vendors Cisco, Proxim, Motorola, etc). The only downside I found concerns the material on the CD that is included with the book. While it does come with sample tests and flash cards I found a few of the questions to be incorrect, another reason to purchase the online practice tests.
Now the material on this exam are the fundamental basics of a WLAN (pertaining to the 802.11 standards, the RF spectrum, and WLAN hardware) and because of that I really do recommend this to any type IT professional who is new to working with WLANs. Whether you are help desk/field technician or even a network administrator that needs to support/implement a new WLAN this book does deserve at least one look over. When I first started working with WLANs I would have loved to have this book it would have saved me hours of research back then. However if you are like me and you have plenty of experience with wireless already I would skip the CWTS and go straight for the CWNA certification.
Now that’s a rap for the CWTS, considering my experience with this exam and the material, I will be pursuing my CWNA certification later on this year but I want to squeeze in a lot of study time for the CCDA exam before Cisco retires the 640-863 April 30th. It’s a certification I tried pursuing a long time ago but just never dedicated that much time to, however between then and now I’ve read many Cisco design guides and both 640-863 Cisco Press books. So if you notice my upcoming entries leaning more towards network design consideration that’s why.
While LWAPs and Wireless Controllers can streamline and standardize WLAN deployments, it also tends to provide a not so nifty single point of failure. If you only have one WLC in your network and you lose all connectivity to that WLC, whether it be a mis-configuration or a general failure all your LWAP’s will go down until they can join the controller again (or find another controller to join).
The configuration for this is actually fairly simple (especially if you only have 2 WLC’s). First off you want to issue the sh mobility summary to go over the current mobility settings, all these settings are important but probably the most important one is the Default Mobility Domain this is the current name of the mobility group and both controllers will need to be in the same mobility group. (Important: Mobility group names are case-sensitive). If you wish you can change the mobility domain name by issuing the follow command config mobility group name group_name command.
Now once you’ve decided on a mobility group name and both controllers are in the same mobility group, you need to add each respective controller’s MAC address and IP Address as a member of the mobility group on all participating controllers. This done with the following command config mobility group member add mac_address ip_address. Mobility group members can be removed by changing the add keyword with the word delete. Now, each model of Cisco WLC’s can support a max number of 24 mobility group members. So their is a limit, albeit a fairly large limit but it does exist.
Also keep in mind, all this can be done via the GUI interface under Controller -> Mobility Management and of course in the GUI everything is pretty self-explanatory in labelled fields for you to configure easier. (Just more time-consuming)
Once this is all said and done you want to issue the sh mobility summary again to verify the configuration and verify the status of each mobility group member is up.
A few facts to keep in the back of your mind are mobility group messages communicate over UDP port 16666, you will want to create rules or an ACL allowing that kind of traffic between the controllers (If you have any type of firewalls between them). You can issue the following commands to very connectivity ping, eping, mping. Obviously the ping command is just there to verify layer 1 connectivity, eping will verify the EoIP tunnel between the controller has formed. The EoIP (Ethernet of IP) tunnel is where all these mobility messages are exchanged through, and mping will test communication over UDP 16666.
Note: I would have loved to include my own screen shots, but I do not have 2 WLC’s out of production to work with.