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New Member

Rapidly increasing output drops on Dot11Radio interface

Hello all,

Our monitoring system detected rapidly increasing output drops on Dot11Radio interface for 3 Access Points at a customer site. Here is the simplified output confirming it from the AP:

AP-1#sh int do0 | i drop

  Input queue: 0/1127/351/0 (size/max/drops/flushes); Total output drops: 1719738176

AP-1#sh int do0 | i drop

  Input queue: 0/1127/351/0 (size/max/drops/flushes); Total output drops: 1719738384

AP-1#sh int do0 | i drop

  Input queue: 0/1127/351/0 (size/max/drops/flushes); Total output drops: 1719738466

AP-1#sh int do0 | i drop

  Input queue: 0/1127/351/0 (size/max/drops/flushes); Total output drops: 1719738616

AP-1#sh int do0 | i drop

  Input queue: 0/1127/351/0 (size/max/drops/flushes); Total output drops: 1719738686

AP-1#sh int do0 | i drop

  Input queue: 0/1127/351/0 (size/max/drops/flushes); Total output drops: 1719738770

AP-1#sh int do0 | i drop

  Input queue: 0/1127/351/0 (size/max/drops/flushes); Total output drops: 1719738828

AP-1#sh int do0 | i drop

  Input queue: 0/1127/351/0 (size/max/drops/flushes); Total output drops: 1719738900

The above commands were executed 1 second from the previous one.

Here's the interface config:

AP-1#sh run int do0

Building configuration...

Current configuration : 504 bytes

!

interface Dot11Radio0

no ip address

no ip route-cache

!

ssid HW-WLAN

!

no short-slot-time

speed  basic-1.0 basic-2.0 basic-5.5 basic-11.0 6.0 9.0 12.0 18.0 24.0 36.0 48.0

no preamble-short

channel least-congested 2412 2417 2422 2427 2432 2437 2442 2447 2452 2457

station-role root

rts threshold 2312

no dot11 extension aironet

bridge-group 1

bridge-group 1 block-unknown-source

no bridge-group 1 source-learning

no bridge-group 1 unicast-flooding

bridge-group 1 spanning-disabled

end

Can someone please suggest where do I start troubleshooting this?

16 REPLIES
Hall of Fame Super Gold

Rapidly increasing output drops on Dot11Radio interface

Hmmm ... 2.4Ghz radio.

Could be cause by a few things:

1.  Channel interferrence; or

2.  Weak signal

New Member

Rapidly increasing output drops on Dot11Radio interface

Thanks for your reply. I don't recall anyone at the site complaining of weak wireless. How do I check it?

Hall of Fame Super Gold

Re: Rapidly increasing output drops on Dot11Radio interface

On the WAP, use the command "sh dot11 assoc" will tell you the client, run the command again but at the end enter the MAC address of the client and look under "Signal Strength".  You want a low negative number.  Anything higher than -75 dBm is baaaaaaaaaaaaaaaaaaaad.

New Member

Re: Rapidly increasing output drops on Dot11Radio interface

Well it kept fluctuating, but I believe this one shows the average:

AP-1#sh dot11 associations all-client | i Strength

Signal Strength   : -46  dBm           Connected for    : 1771 seconds

Signal Strength   : -67  dBm           Connected for    : 14286 seconds

Signal Strength   : -35  dBm           Connected for    : 50001 seconds

Any suggestions on checking channel interference?

Hall of Fame Super Gold

Rapidly increasing output drops on Dot11Radio interface

Any suggestions on checking channel interference?

Commands are:  dot11 dot110/dot111 carrier busy

Results will appear in the "sh logs".

New Member

Re: Rapidly increasing output drops on Dot11Radio interface

I got this in the show log

Frequency  Carrier Busy %

---------  --------------

   2412          1

   2417          3

   2422          1

   2427          0

   2432          2

   2437          1

   2442          1

   2447          0

   2452          0

   2457          0

   2462          0

   2467          0

   2472          0

Does it make sense to you?

Hall of Fame Super Gold

Rapidly increasing output drops on Dot11Radio interface

Makes alot of sense.  The low number on the right-hand side means that the channels are not "busy" or little interferrence.  How about the others?

New Member

Rapidly increasing output drops on Dot11Radio interface

Do you mean other AP's? This AP is the one showing the maximum rate of output drops. The others show much lesser than this one, so I would like to focus on this one first if its okay

Re: Rapidly increasing output drops on Dot11Radio interface

I did a blog post that might help you understand carrier busy ...

http://www.my80211.com/cisco-auton-cli-commands/2010/6/20/autonomous-carrier-busy-test.html

__________________________________________________________________________________________ "Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin ___________________________________________________________
New Member

Rapidly increasing output drops on Dot11Radio interface

Excellent post. Really informative.

I typed "dot11 dot11radio0 carrier busy". Do I need to do it for dot11radio1 too?

Rapidly increasing output drops on Dot11Radio interface

0 is your 2.4 Ghz radio and 1 is your 5 GHz radio.

__________________________________________________________________________________________ "Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin ___________________________________________________________
New Member

Re: Rapidly increasing output drops on Dot11Radio interface

Ok I get it. 5 GHz is not being used as I see the interface is admin down

Dot11Radio1                unassigned      YES NVRAM  administratively down down

What else can I check?

New Member

Rapidly increasing output drops on Dot11Radio interface

Anyone having any more ideas which I can try?

New Member

Rapidly increasing output drops on Dot11Radio interface

Bump...

Anyone?

Re: Rapidly increasing output drops on Dot11Radio interface

it's hard to say. It could be interference but without a spectrum check we cannot rule in or out that. Can you move the clients to 5ghz for a test? And this started all of a sudden? And clients are getting disconnected and slow connections?

Sent from Cisco Technical Support iPad App

__________________________________________________________________________________________ "Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin ___________________________________________________________
New Member

Re: Rapidly increasing output drops on Dot11Radio interface

The users haven't reported any major issues. Their connections don't drop. Any helpful links detailing how to go about checking the spectrum? I'm afraid the 5 GHz test wont be an option as its a production network.

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