ā01-28-2018 02:33 PM - edited ā07-05-2021 08:10 AM
Capwap packets from some access points are getting set to DSCP 46 when traversing the distribution switches.
I was troubleshooting a slow download issue when we noticed this occurring. The odd part is if I replace any of the access points with a spare the problem no longer occurs.
Any idea how the access point can determine if the distribution switch changes the cpawp packet to DSCP 46?
WLC = 5520
Access point=2702i
Closet switch=3750
Distribution switch = 6509 Sup2t
ā01-28-2018 06:04 PM - edited ā01-28-2018 06:08 PM
Did you check what is that capwap traffic ? If it is CAPWAP control traffic (UDP 5246) then it will be marked as CS6
If it is CAPWAP data traffic then check below.
Is there any classification ACL on that 6500 to macth that AP to WLC traffic and mark it as EF ?
If possible share any policy-map configs associated to the switchport connecting to downstream switch where directly connected APs.
HTH
Rasika
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ā01-29-2018 09:02 AM
We are testing with iperf all capwap packets are getting marked EF. You can see in the trace were the inner IP header is marked 0 and the outer is marked 46. We also notice that our distribution switch is marking the packet but I don't know why. I replaced one of the access points and the problem stopped for that access point.
ā02-04-2018 04:17 PM
Hi Steve
"You can see in the trace were the inner IP header is marked 0 and the outer is marked 46"
If this is happening with different APs, I would check how you configure QoS on your WLC. Hope you have configured "Trust DSCP Upstream" with enabling QoS map ( Wireless > QoS > QoS map > Trust DSCP upstream)
With that setting, for uptream inner DSCP should be copied to outer CAPWAP DSCP. Watch below Ciscolive presentation for more details
QoS Design and Deployment for Wireless LANs - BRKRST-2515
"We also notice that our distribution switch is marking the packet but I don't know why. I replaced one of the access points and the problem stopped for that access point"
If you replace an AP & it fix the issue, that is really odd. Unless that AP is really doing something strange.
HTH
Rasika
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ā02-05-2018 07:26 PM
Thank you for your reply. We found the issue. The Access points use different ephemeral port based on their Mac. We match on a small portion of these port with our voice access list. This was causing our core router to mark up the capwap packets to 46. I am going to move the wireless policy map to the top so the capwap packets will be trusted before being marked up.
ā09-23-2019 05:40 AM
Hi Rasika
I am observing this same issue with all CAPWAP traffic being marked with DSCP 46.
Do you have a link to explain the motivations behind enabling the QoS mapping and the trusting of upstream DSCP?
My customer currently has the Platinum QoS profile enabled with AVC profiling. QoS mapping is disabled
Many thanks
Ashley
ā09-23-2019 11:09 AM
Hi Ashley,
Pls go through below ciscolive presentation to get good grasp of wireless QoS
BRKRST-2515 QoS Design & Deployment for Wireless LAN
HTH
Rasika
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ā09-25-2019 01:31 AM
Thanks Rasika
The presentation was very helpful! It looks like our problem was due to the Wireless QoS Peramiter defaults being set to VOICE for unicast and multicast.
Cheers
Ashley
ā01-29-2018 09:12 AM
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