Slow Guest speed traffic

[Nando5]

Good morning Cisco heads! 

I have an ongoing issue whereby the Guest internet traffic and LAN traffic is traversing the same Internet WAN link but wireless users are experiencing slowness on the Guest traffic connected to the WAPs but users connected to LAN (Ethernet) speeds are fast and optimal. I have upgraded the WAPs firmware, I've done a reboot of the Internet switch and Firewall and still its slow. Sometimes the Guest Wi-Fi speeds will reach desired speeds but its very sporadic. All WAPs are connected directly to the external internet switch but LAN users are connecting to access switch feeding to the core switch. I just cant seem to understand why the Guest Wi-Fi will be slow if its going through the same internet link as the LAN. If it was a ISP issue then all users would experience slowness. I'm using checkpoint firewalls and cisco switches. 

Much Appreciated.

[Joseph W. Doherty]

Wireless, itself, can be "slow" for many reasons.

If using LWAPs, rather than WAPs, they have other possible issues.

[liviu.gheorghe]

Wireless throughput can depend on many factors - Data rate/Modulation being one of them.

Another factor is the band used by the wireless client, 2.4 GHz or 5 GHz. In 2.4 GHz the data rates are lower, but it covers a greater distance from the AP. For 5 GHz the data rates are higher, but the distance from the AP is lower.

Another factor is RSSI and SNR - as these values get smaller, meaning that the wireless client moves away from the AP or some obstructions is in between, so does the data rate of the wireless client.

[pieterh]

are these stand-alone access points or controller based access points ?
if controller based, then guests wifi is forwarded through a capwap tunnel to the wireless controller
the controller "drops" the packets to the internet.
there may evan be an "anchor controller" in a DMZ involved
if this is the case , it does not matter the accesspoints are on the samw switch as the internet connection,
but is is important where the controller is connected.

make a diagram of your network and investigate deeper how your guest network reaches the internet
and provide more information to help analyze the problem

[Joseph W. Doherty]

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@pieterh wrote:

if controller based, then guests wifi is forwarded through a capwap tunnel to the wireless controller

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Indeed!  One of the many reasons I had in mind.

Such CAPWAP tunnels, can also lead to packet fragmentation.  Two ways to mitigate that, if controller supports, it can adjust max MSS to avoid fragmentation of TCP packets, or, if wired network supports jumbo Ethernet, 1500 byte packets, when tunneled, will not need to be fragmented.

Again, many other possible reasons for slow wireless.

[Joseph W. Doherty]

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@liviu.gheorghe wrote:

Wireless throughput can depend on many factors - Data rate/Modulation being one of them.

Indeed!  One of the many reasons I had in mind.

I recall, one issue with multiple wireless modulation rates, being used on the same AP, not only is a client using a slower modulation rate slower, it also slows all the other concurrent clients using faster modulation rates.  Remember, wireless bandwidth is shared, conceptionally much like a wired hub.  (Oh, and also like a wired hub, number of clients using an WAP, and how active each client is, hugely impacts performance too.)

Some performance recommendations for wireless, suggest disabling supporting older/slower modulation rates.

Again, many other possible reasons for slow wireless.

[Leo Laohoo]

Is QoS enabled on the SSID or "per user"?