Fluctuating Ping

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  • Updated 4 years ago
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I have deployed a Zonedirector 1100 and 6 x zf7372 APs. The APs are connected to the same PoE switch as the ZoneDirector.

APs are not configured for mesh mode.

Signal coverage is good, but I am getting fluctuating pings when testing from various devices - it follows the pattern 1 good ping (1ms), 1 average pint (~100ms), then one higher ping (200-300ms) - then repeat.

For testing I am pinging the IP address of the ZoneDirector to eliminate any other network issues. Checking the logs it shows the channel selection and client association to be static - I am not moving around but in a fixed position and the ZD reports this to be accurate:

Reply from 10.10.1.20: bytes=32 time=2ms TTL=64
Reply from 10.10.1.20: bytes=32 time=10ms TTL=64
Reply from 10.10.1.20: bytes=32 time=211ms TTL=64
Reply from 10.10.1.20: bytes=32 time=136ms TTL=64
Reply from 10.10.1.20: bytes=32 time<1ms TTL=64
Reply from 10.10.1.20: bytes=32 time=2ms TTL=64
Reply from 10.10.1.20: bytes=32 time=133ms TTL=64
Reply from 10.10.1.20: bytes=32 time=10ms TTL=64
Reply from 10.10.1.20: bytes=32 time=249ms TTL=64
Reply from 10.10.1.20: bytes=32 time=2ms TTL=64

I have tested on both 2.4GHz and 5GHz channels but I get the same result.
The pings never drop and I get good throughput when transferring data, but I am not sure the latency should fluctuate as much as this.

Firmware on ZD is the latest ( 9.6.1.0 build 15)
Does anyone have any ideas?

Thanks
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Adam Carter

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Posted 4 years ago

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Keith - Pack Leader

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Try repeat traceroutes. My suspicion is you are seeing a routing issue.
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Adam Carter

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Thanks for the reply Keith - after some further investigation last night I found the issue - my laptop. I disabled and then re-enabled the wireless interface causing it to re-associate with the wireless network and then the issues were magically solved. Rock steady 1-2ms pings when stationary and when roaming about :) It doesn't explain why it happened, but other devices are now connecting and not showing the same symptoms.

Large humble pie just eaten for breakfast!
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Keith - Pack Leader

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Adam - truly appreciate you sharing this (esp with the pie). These discussions are helping hundreds of other customers fix or avoid similar issues so it's always nice to hear the resolution.
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Greg Morgan

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I am having this exact issue. Have you had no further issues since disabling and renabling your wireless card Adam? I have never experienced this with any other AP, it's a bit of a concern...
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Adam Carter

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Unfortunately I don't have remote connectivity to that site so I can't test it with my laptop again - but I have had feedback from other users there and they can hold a much more steady ping than I originally did. Sorry I can't be much more help - can you reproduce it on another device?
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Michael Brado, Official Rep

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Check to be sure there is no routing/switching loops between AP and ZD on the
network, as this has been seen to cause every other ping speed fluctuations in
past cases.
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Greg Morgan

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Hi Michael. There is no ZD in the mix and I was experiencing this pinging a standalone AP not connected to a switch.
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Keith - Pack Leader

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Greg, you are saying that disabling/enabling the wireless card didn't work, or have you not tried that yet? If not, please do try and report back. If it works, the problem lies with the wireless card (driver) in the PC.

If it does not work, make sure there is no chance of a duplicate IP or loop *anywhere* in the network.
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Greg Morgan

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Hi Keith,

I did try that and it did not work. There is nothing else/no duplicate ip's in the network, only 1xAP and my laptop, neither plugged into a switch. I am not having this problem at any other client so my laptop is fine. I have tried with another AP and have the same result. It looks to me like interference but I have never seen latency this high before.
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Adam Carter

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It does look like interference - have you done a wireless scan to see if there is anything else broadcasting on the same (or close) channel?
If not is there anything else that could be transmitting on a similar frequency or generating a lot of noise (think microwave,cordless phones, electrical motors).
Also try moving the AP to a new location to rule out environmental factors
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Greg Morgan

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Hi Adam,

I think I've found the problem. I'm using InSSIDer to monitor coverage and interference from other AP's. I've realised that when this application is open, my pings sky-rocket. This makes sense because the application obviously also sends pings to the AP to provide real-time RSL levels.
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Greg Morgan

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Hi Adam,

I think I've found the problem. I'm using InSSIDer to monitor coverage and interference from other AP's. I've realised that when this application is open, my pings sky-rocket. This makes sense because the application obviously also sends pings to the AP to provide real-time RSL levels.
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Adam Carter

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Ah - you probably shouldn't be scanning and testing throughput on the same wireless interface at the same time ;)
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Greg Morgan

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You learn something new everyday... Well thanks for all your help guys.
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Keith - Pack Leader

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Glad to hear you found the issue, and especially appreciate you sharing it.

Ping is a great way to test connectivity, but that's about all it's good for. ICMP response are generally given very low priority - so if a system is busy that's the first thing it will drop - even when other traffic is running smoothly (this is true of almost anything with a network interface, not just our gear). It works best as a diagnostic when the packets transit the suspect device rather than terminate there.