Welcome to the Cisco Networking Professionals Ask the Expert conversation. This is an opportunity to discuss Wireless Networking Including Hot Spot Access with Cisco expert Christophe Servais. Christophe leads WLAN Public Access marketing for Cisco Systems, Inc., covering 802.11, GPRS & 3G and associated infrastructure technologies. He works closely with design and deployment of WLAN and Public Access deployments. Feel free to post any questions relating to Wireless Networking Including Hot Spot Access. Remember to use the rating system to let Christophe know if youve received an adequate response.
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Does anybody know useful links, reference book and/or docs that help me preparing for WLANFE certification? So far I tried on different resources but could not find any reference book that provide inside of technology and can be use as reference for WLANFE certification.
There's currently no reference book recommended for this certification, only courses (web based and instructor led).
For more information, you can check :
Besides, I suggest to check the solutions and products links proposed on this page.
We have over 200 802.11b installations usings 350's and 1200's. Some installations are concentrated in our main offices and some are located in smaller field offices. Firmware is mostly 11.21 and 11.56 respectively.
On about 10% of the installations we are getting "Packet Error is in Overloaded state (100%)" for the radio interface. There does not appear to be a common denominator.
I would need more information here to comment. Does it happen where you have mixed (350 and 1200 - soft versions) environment ? What is the actual WLAN behavior ? Have you checked that the spectrum is clean of interferences ?
We saw the problem before 1200's were added to the system and before we upgraded firmware to the current versions. I'm not sure what you mean by WLAN behavior. The affected AP's are working but we have such light usage that I doubt a user would notice reduced throughput. As to clean spectrum, no, we have not checked but some of these unit are in remote locations. Our spectrum analyzers are good at fixed frequencies but do not see spread spectrum signals. I have allowed the AP's in some cases to "search for a less congested frequency" and it has helped in some cases but not in others. I'm using the WLSE and have had to move the threshold for this alarm way up to avoid large numbers of log entries.
Send your email address and I'll send some representative traffic graphs.
We are trying to implement VLANs on aironet 1200s. I am currently using Nortel's VPN client for security, when on our open VLAN. When I roam from one AP to another AP on the same subnet I have no problem, but when I am trying to roam to a different AP on a different subnet I lose the tunnel connection. IS there any documentation, or HW/SW that will enable me to roam to different APs on different subnets while using VPN as security on a open wireless VLAN.
VPN is certainly not the easiest nor the most flexible way to implement WLAN security. This is one of the benefits of 802.1x and TKIP to provide a secure link and keep the network open for features rich environment.
Having said that, when you say that you move from one subnet to another - I guess it's different APs on different IP subnets (L3), right ? Same open VLAN ?
If so, 802.11 has not been designed to handle L3 roaming, VPN or not, and you have to implement mobile IP.
Then VPN over Mobile IP has to be configured but here, I could guide you with a Cisco VPN solution.
Let me know if my understanding of your question is correct and I'll provide you with links to configuration documents.
Yes your reasoning is correct. Any documentation you could send would be extremely helpful!
I work at a large hospital and our goal is to provide wireless access for patients. Employees currently have wireless access. I am trying to do multiple vlans on one access point. A vlan for patients, one for employees and one for managing the access point. All looks good except "Virtual-Dot11Radio This interface is down along with the sub interfaces that belong to it. What does this Virtual-Dot11Radio do? Or where can I learn more about it.
Based on your question I take it you have an IOS version of our AP
You'll find everything related to VLAN configurations at :
Then check page 13-6 and after.
Does your switch support automatic 802.1q/trunk negociation ? What is the soft version of your AP ?
I work with Virgin Technologies, Nigeria. I had a problem many months back. I installed a Pt-2-Pt link using a FHSS wireless bridge called Raylink. This bridge was meant to carry 512k of data, and the throughput of the bridge was 2MB. But the bridge kept dropping packets.
My second question is if heliax cable of about 60metres connected from a highly directional grid antenna to e wireless bridge unit will work? Since Heliax is a low loss, high frequency cable.
Regarding your Raylink bridge, several problems can explain such a behavior, including bridge failure. You mention the problem as being in the past so I take it it's no longer one ?
Regarding the cable, as long as it's designed to carry the right frequencies, the max length is a result of a calculation. The parameters will be the power of transmission - the Tx and Rx antenna gain - the path loss (distance) - and the sensitivity of the bridges. If with Cisco's gears, you can use our calculator :
I have a question about the 1200 series radios and using them as repeaters. I want to have one AP with an a radio only set as a Root AP connected to the wired LAN. I want to then take another AP with an a and a b radio and set it as a repeater. My question is, with this setup, will the b traffic on the repeater AP route through the a radio and then onto the network through the first AP?
That is an interesting and creative idea. I guess that you want to aggregate repeaters around one root access point and take the benefit of the 5GHz links to avoid bandwidth degradation.
The two AP1200 radios are mapped internally so, yes, the traffic will be routed. Make sure you have a consistent security configuration (802.11a side and 802.11b side).
Such a configuration hasn't been fully tested yet. You might want to manage, at the network level, the downlink datarate to avoid congestion at the AP repeater level.
I have a lot of aironet 340 bridges that we can't get power supplies for anymore. Is there a source for these power supplies? Also we are replacing them and adding aironet 350's. Are the 2 compatible to use as bridges together???
Unfortunately, we don't know of any source for your 340 bridges power supply.
The BR350s and BR340s are not compatible over the air.
If the two APs are on the same IP subnet (Layer 2 roaming) : no problem.
If the two APs are on different subnets (Layer 3 roaming), you have to implement Mobile IP and then run a VPN tunel over Mobile IP.
ISP customer is using several BR350 devices in its network, and one of them is experiencing the following problem:
The bridge is working as a repeater, but stops forwarding occasionally (about once a day now). When this happen they can see that the bridge has changed its role to Site Survey Client.
What could cause this behavior?
Well ... this would need an analyse of the network. What is the software version of the bridge ?
When trying to use the APs for point-to-multipoint purposes, with 1 building acting as a central node, and a couple of remote sites 3.8 miles away from it, what would be a suitable antenna to accomplish a clean, drop free 3Mbps connection?