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Cisco Wireless: High Ping response time to gateway/local switch

dot1x
Level 3
Level 3

Hi Experts,

I have configured a Cisco wireless network using 5508 WLC with bunch of 3800 APs in Flexconnect mode (local switching).

Everything works fine but the ping response to gateway/local switch is too high.

I noticed that when the Wireless network is idle, I see high ping latency. When there is some activity on the network, say I'm downloading something or making a call over WLAN, the ping response gets back to normal.

Could someone help here?

13 Replies 13

Leo Laohoo
Hall of Fame
Hall of Fame

I noticed that when the Wireless network is idle, I see high ping latency. When there is some activity on the network, say I'm downloading something or making a call over WLAN, the ping response gets back to normal.

I see this when pinging 792X VoWLAN handsets.  If not being used, the ping time is high.  When in use the ping time is low. 

This is deliberate.

Hi Leo,

Thanks for your quick response.

Could you elaborate a bit for me please?

I'm pinging the local switch IP from my laptop and I see high latency.

As soon as I start any activity on the network, the ping gets better.

On WLC, the Channel utilization and interference is under 10%.

I'm pinging the local switch IP from my laptop and I see high latency.

I presume the laptop is on wireless?

Yes, it is.

Tried to ping local switch the AP is connected to.

To add to Leo's point, try different devices to see if the issue is the same. At least that way you can isolate the issue to a specific client device type, NIC or driver. If another device doesn't have that issue, well I would have to say that there is nothing wrong with the wireless, but something with the client. 

-Scott 

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-Scott
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Thanks Scott,

Checked with different clients too.

I have read somewhere that the client NIC goes to sleep mode when there's no network activity and would give least priority to ping packets.

If that's the case, can we fine tune NIC and prevent it to go to sleep?

In Wireless NIC properties, I 'unchecked' the option 'Allow the computer to turn off this device to save power', the issue still persists.

It really depends on the device. If the device is being used and there is high ping times, I would also assume the user is noticing that. Now this is most like a drive issue and you can try to upgrade or downgrade if necessary. You can also try to use an external NIC to see if the issu is related to the internal NIC to help isolat the issue. Don't use ping to determine if wireless is good or bad. Use it as a reference point but also understand that if the driver does what you are saying, probably there is not workaround for that. I have not ran into that issue... so out of curiosity, what laptop, OS, NIC and driver

-Scott 

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-Scott
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Hi Scott,

So I did some testing on-site.
I found out that whenever a user roams from one AP to other, the ping latency is observed for few seconds.

Though it doesn't affect the network connectivity, but there were few users who were concerned about it.

Is this normal when switching between APs?

It can be, what are they seeing when they roam?  How high is high?  It's hard to say if this is expected without really knowing how your network is designed and how sparse or dense the environment is.  Try to run some pings and roam from one AP to another that you know is close by and then another area which an AP is further out. Get some baselines so you have an understanding. Also don't run any apps, reboot the laptop and then issue a continuous ping.  This can help also determine if an app is making the device sticky or not.  

If you get a few pings that are high, that would be normal. In some cases also, you might get a ping timeout. With these results, you can determine by your AP placements if they are good, bad or okay. Roaming decisions are made by what AP the client can hear without using any features. If the user experience is not affected, then what you are seeing is not an issue I would say. 

-Scott 

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-Scott
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How high is high?

6 to 8 ping responses somewhere between 400ms to 600ms or/and a couple of timed out pings when roaming from one AP to other.

Also don't run any apps, reboot the laptop and then issue a continuous ping.

Not running any Apps and it's new deployment, so there're no other users on the floor.

Moin,

Dont know what the issue might be unless it's with that specific device(s).  You did mention that this happens with other devices also.  Have you disabled the lower data rates?  Like Leo mentioned? What NIC and driver version?

Have you tried to create a test SSID that is just open and see if that has issues?  Make sure you don't make changes to the wlan just set it to open auth.

-Scott 

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-Scott
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If you get a few pings that are high, that would be normal. In some cases also, you might get a ping timeout.

That what the issue was. This didn't affect the network performance, it's just a couple of users were concerned.

As of now network works fine.

Thanks guys for your inputs!

What is the exact wireless NIC model and the version the driver is running on?

What OS is the laptop?