Client took time to grab the DNS during rooming

[mohammad saeed]

Hi Guys,

I have WLC 8.3.122.0 and there are around 245 AP join the wlc. I noticed the issue when the client move from AP to another AP I noticed that the DNS removed and take long time for client to access the internet around 2 minutes. 

What could be the issue here?

Thanks for all

[Scott Fella]

When a device roams in a good wireless system, the device will keep its up address and all dhcp settings like dns. I have never seen a device loose dns that has a valid ip or has not done another reauth. Are you sure that the device isn’t performing a full re-association? If so, then either your roaming is broke or you have a very sparse ap deployment.

[mohammad saeed]

Actually I was testing with LG Android phone and I noticed this issue! I will try it with iPhone and another kind of phone to see where is the problem! because it's weird to me just only DNS IP released and IP address of client still the same only DNS released and waiting for to get it again.

[Scott Fella]

When doing any type of wireless troubleshooting, you always want to check if the issues is with all, few or only one device. Or one type. This helps isolating the issue. Now since you mentioned LG, maybe make sure the settings/drivers are good and make sure the device doesn’t have Mac address randomizing turned on.

[mohammad saeed]

Thanks for advice..definitly thats what I am going to do.

[mohammad saeed]

I tried today with Samsung phone, during roaming the signal with limited access fr a while "no internet" during roaming then have internet access! I am not sure what is the issue here! firs time happened with me! 

[Scott Fella]

Well if you open a TAC case , they will tell you to upgrade. 8.5 is a good code if your AP’s support that version. Might be something you need to try.

[mohammad saeed]

Yes that is what I am trying to try is to change the SW version but I m confused if this will effect on the Redundancy WLC and if my APs supported!

the AP model are two type: 

AIR-CAP1602E-E-K9

AIR-CAP2702E-E-K9

[Scott Fella]

The matrix will show you what codes are compatible with what devices. This is the key document to follow before purchasing any new devices or trying to upgrade.

https://www.cisco.com/c/en/us/td/docs/wireless/compatibility/matrix/compatibility-matrix.html

Look at the matrix and figure out what code is supported by your access points.