WIFI Throughput not what it should be

pendal8286 · ‎03-26-2019

Hello all and thanks for your time and expertise. I have to troubleshoot a WIFI issue tomorrow. One of my fellow techs indicated the WIFI throughput is poor in a building we support. Please note the APs in this building were recently installed so coverage should not be an issue. We made sure each room was sufficiently covered. Further, he indicated the signal is strong in the room but the throughput is poor.

I'm looking for recommendations relative to troubleshooting. The building only has three switches and I'm pretty sure the edge switch was recently made the root bridge for the building's network. I guess another tech thought there may have been an STP problem.

Should I start with a packet analyzer on the network and see what that shows? I'll make sure the WIFI signal is indeed strong and there's no appreciable interference but is the packet analyzer the next logical step? Sorry for the general information but this is all I have for the the time being. Appreciate the insight and recommendations.

Dennis Mink · ‎03-26-2019

i would start by quantifying, what throughput means and how was it tested to conclude that it is a problem, so you can reproduce the issue. maybe use iperf to simulate traffic through out through the day to see if there is any performance degradation over time.

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Scott Fella · ‎03-26-2019

Just to add, look at your experience and also ask various users. Everyone has a different tolerance.

I would review the configuration and AP placements first since you will be onsite. Then look at the various devices and driver versions and also determine what band they are connected to. This will help isolate issues much faster. Spectrum Analyzer helps if you have an unknown interfere or want to identify interference and noise. Remember to also test in various locations and speak with users in various locations also.

-Scott
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luis_cordova · ‎03-26-2019

Hi @pendal8286 ,

Check this guide, maybe can give you some help:

https://community.cisco.com/t5/wireless-mobility-documents/wireless-throughput-testing-guide/ta-p/3143894

Regards

Leo Laohoo · ‎03-26-2019

@pendal8286 wrote:

Further, he indicated the signal is strong in the room but the throughput is poor.

What radio was he connected to? 2.4 Ghz or 5.0 Ghz?

What was the RSSI and SNR value?

How did he come to the conclusion? What "metrics" or methods did he use? Try www.fast.com.

pendal8286 · ‎03-27-2019

Fellas, thanks for the great replies. I'm going to work on this problem tomorrow and I'll follow-up. Thanks.

pendal8286 · ‎03-29-2019

Hello all. Just wanted to let you know how things went yesterday. So I ran iperf in one of our buildings and the throughput was 256 mbits. In the building I'm testing, and the equipment and APs are the same, the throughput was around 80 to 90 mbits. And when I went to fast.com and tested the throughput to the internet - the levels were all over the place on three floors. On the first floor the throughput was around 20 mbits. On the second floor the speed was around 80 mbits and the same for the third floor. I also ran a network tester for interference and the levels were low.

However, when I checked the switches, and specifically the VTP configuration - I noticed the VLANS, and specifically the IP address configuration, is not propagating to the other switches. In other words we have a vlan 218 created on the vtp server (the core.) The vlan name (and IP helper address) have propagated to the other switches but not the ip configuration assigned to vlan 218. And this is the same status for all of the vlans.

That said I made sure the vtp domain are the same on all the switches as well as the configuration revision and there's no password set. I tried creating a new vlan and changing the domain name to get the vlan information to propagate but no luck. I've never seen a scenario where the vlan names propagated but not the ip configuration assigned to the vlans.

I also confirmed the trunks are configured correctly.

Anyway, if anyone has any ideas please let me know because I've never experienced this scenario before. Thanks.

Leo Laohoo · ‎03-29-2019

If the VLAN DB wasn't propagating properly the APs wouldn't work.
Can you describe how are the buildings interconnected? Can you check to make sure there are no speed &/or duplex errors to the uplinks?

pendal8286 · ‎04-04-2019

It turned out some Quality of Service options were the problem. Thank you.