Can someone block this guy? Not for hijacking a question (which is rude), but the idea of "rea l lab questions" smells of "actual lab questions" which is illegal and can be cause for removal of your Cisco certifications and blocking from obtaining the CCIE.
Jason Boyers, CCIE #26024 (Wireless) Blog: netboyers.wordpress.com On Thu, Sep 12, 2013 at 3:47 PM, john arther <[email protected]>wrote: > Hi, > > If anyone want to pass CCIE WIRELESS LAB then lets discuss on rea l lab > questions and work on it lets break the lab share the questions and > solutions > > Add me on skype id is (*quad.quad4*) > > Thanks > > > On Thu, Sep 12, 2013 at 7:17 PM, Jeen Sern Chew <[email protected]>wrote: > >> Thanks Jason and Jeff, >> >> It is really confusing, especially with conflicting information out >> there, like with the hysteresis of being 3 dBm both ways or 3 dBm one and >> 6dBm the other. >> >> Also after calculating, how would you know to increase or decrease the >> power? >> >> The following is how I understand it after some thinking. Some of the >> figures are just base on real world experience. Say you do a voice survey >> and place your APs to provide coverage of -67 dBm, 20% overlap and power >> level of 6-25 mW. The following are the assumptions: >> - Cisco formula as mentioned above is correct >> - TPC only decreases power >> - Hysteresis of 3 dBm >> - There's another APs see each other rather than by transmitting >> neighbour message at full power >> >> Starts off at level 1 / 100mW. I chose the 3rd highest RSSI to be -50 dBm >> as that would happen in a voice/high density survey. >> >> 20 - (-67 - (-50)) = 20 - (-17) = 37 Hysteresis met, decrease >> from level 1 / 20dB to level 2 / 17dB >> 20 - (-67 - (-60)) = 20 - (-7) = 27 Hysteresis met, decrease >> from level 2 / 17dB to level 3 / 14dB >> 20 - (-67 - (-70)) = 20 - 3 = 17 Hysteresis met, decrease >> from level 3 / 14dB to level 4 / 11dB >> 20 - (-67 - (-80)) = 20 - 13 = 7 Hysteresis met, decrease >> from level 4 / 11dB to level 5 / 9dB >> 20 - (-67 - (-85)) = 20 - 18 = 2 Hysteresis not met. Stay >> at level 5 / 9dB >> >> At level 5, it is close to the figures of some deployments out there. >> >> Does this calculation make sense? Did I miss anything? If it correct, >> great! Just need to confirm the assumptions above then. >> >> Thanks >> J Chew >> >> >> On 12 September 2013 01:39, Jeff Rensink <[email protected]> wrote: >> >>> This is a frustrating topic indeed. >>> >>> TPC will do both power decreases and increases as the environment >>> changes. But the formula that the document references has a flaw that I >>> haven't totally reconciled. >>> >>> Tx_Max for given AP + (Tx power control thresh – RSSI of 3rd highest >>> neighbor above the threshold) >>> >>> Tx_Max for a given AP should be a static value, correct? It's >>> supposedly the max possible power that the radio can transmit at for its >>> chosen channel. The Tx power control threshold is also a static value that >>> is configurable. So the assumption is that the RSSI of the 3rd loudest >>> neighbor changes along with the current AP power level. >>> >>> If I understand things correctly, the RSSI of the 3rd loudest neighbor >>> is determined by AP neighbor messages. According to documentation (and I >>> believe I've tested this myself), neighbor messages are always sent out at >>> the highest power level and lowest data rate. If that is indeed true, then >>> the RSSI of the third loudest neighbor is yet another static value >>> (assuming the environment isn't changing). >>> >>> So if none of the variables in the equation are actually variable, the >>> results of the equation are always the same. That would mean either the >>> power level would always settle into the max power or the minimum power. >>> That's not true, so something seems off in the equation or the description >>> of the variables in the equation. >>> >>> My guess is the formula is closer to (Max_AP_Power - Current_AP_Power) - >>> (3rd_loudest_neighbor - TPC_Threshold) >>> >>> A positive result would result in a power increase. A negative result >>> would result in a power decrease based on the 3 dBm hysteresis. According >>> to Jerome Henry, it's 3 dBm in both directions in the 7.0.116.0 code. This >>> assumes that the 3rd loudest neighbor measurement is pretty much always the >>> same since neighbor messages are always sent as max power. >>> >>> So let's say we start at full power on the 2.4 GHz band with a 3rd >>> loudest neighbor of -60 and threshold of -67. >>> >>> (20-20)-(-60-(-67)) = 0-7 = -7 >>> >>> -7 is lower than -3, so we drop the power down a level >>> >>> (20-17)-(-60-(-67)) = 3 - 7 = -4 >>> >>> -4 is lower than -3, so we drop the power once more. >>> >>> (20-14)-(-60-(-67)) = 6 - 7 = -1 >>> >>> -1 is not lower than -3, so it doesn't change. >>> >>> This is a total guess, but it makes more sense to me than the formula in >>> the documentation. But in the real world, the higher the TPC threshold, >>> the higher the power levels will be. For instance, a threshold of -60 >>> would result in higher power levels than a threshold of -70. So if you are >>> seeing your APs in a particular location settle in at too high or too low >>> of power levels on average, tweak the threshold as needed. Every increment >>> of 3 should result in powers going up/down one level on average. >>> >>> Jeff Rensink - CCIE #24834 (Wireless, R&S) >>> Senior Technical Instructor - IPexpert >>> >>> >>> On Wed, Sep 11, 2013 at 9:14 AM, Jason Boyers <[email protected]>wrote: >>> >>>> This is a confusing algorithm. Basically, think of it this way: >>>> >>>> 1) Three neighbors (at least) hear an APs radio at or stronger than the >>>> TPC Tx mac value configured under the WLC TPC settings for that PHY >>>> (802.11a/n or 802.11/b/g/n) >>>> 2) If #1 is true, then that formula provided is used. >>>> - The "Tx_Max for given AP" is the maximum transmit power for that >>>> channel on that particular radio. So, for a 2.4GHz radio, that would be >>>> 100mW (20 dBm), since that is the maximum for 802.11b. 5GHz is more >>>> confusing, as it various based on channel and model of AP. >>>> - The "Tx power control thresh" is the value that is entered in the WLC >>>> - Note that there is an "hysteresis" value of 3dB for decreasing and >>>> 6dB (or it was at one point - someone correct me for the current values) >>>> for increasing the power levels. In other words, the value that is given >>>> at the end of the formula has to be at least that dB difference from the >>>> current value in order for a change to occur. >>>> 3) The AP's radio that is heard by the other three APs is the one that >>>> is decreased (or it can be increased) if the hysteresis value is exceeded. >>>> 4) When the formula is run again, it is presumed that the three >>>> neighbors that are hearing the APs signal are hearing a weaker signal. >>>> 5) Keep in mind that the algorithm is always from the perspective of an >>>> AP being heard by 3 or more neighbors, not an AP hearing 3 or more >>>> neighbors. >>>> >>>> Hope this helps. >>>> >>>> Jason Boyers, CCIE #26024 (Wireless) >>>> Blog: netboyers.wordpress.com >>>> >>>> >>>> On Wed, Sep 11, 2013 at 9:36 AM, Jeen Sern Chew <[email protected]>wrote: >>>> >>>>> Hey guys, >>>>> >>>>> I have a TPC question. >>>>> >>>>> There are many conflicting information from different Cisco docs. Some >>>>> say TPC increase and decrease power, some say TPC only decreases power >>>>> while CHD increases power. Does TPC do both or only increase? >>>>> >>>>> Also Cisco gives the TPC formula of: >>>>> Tx_Max for given AP + (Tx power control thresh – RSSI of 3rd highest >>>>> neighbor above the threshold). >>>>> >>>>> Is the Tx_Max is the Tx_Max of the specific AP? or Is it the Tx_Max >>>>> configured on under TPC in WLC? >>>>> >>>>> Also, when the calculation is done, I am assuming the power >>>>> increase/decrease occurs on the neighbour with the third highest RSSI? >>>>> >>>>> Thanks >>>>> >>>>> Regards, >>>>> J Chew >>>>> >>>>> _______________________________________________ >>>>> For more information regarding industry leading CCIE Lab training, >>>>> please visit www.ipexpert.com >>>>> >>>>> Are you a CCNP or CCIE and looking for a job? Check out >>>>> www.PlatinumPlacement.com >>>>> >>>>> >>>> >>>> _______________________________________________ >>>> For more information regarding industry leading CCIE Lab training, >>>> please visit www.ipexpert.com >>>> >>>> Are you a CCNP or CCIE and looking for a job? Check out >>>> www.PlatinumPlacement.com >>>> >>>> >>> >> >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, please >> visit www.ipexpert.com >> >> Are you a CCNP or CCIE and looking for a job? Check out >> www.PlatinumPlacement.com >> >> > > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > > Are you a CCNP or CCIE and looking for a job? Check out > www.PlatinumPlacement.com > >
_______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com
