Manage MTU on Cisco 9166 AP

[GQ_Hub1]

Hello,

I have an AP registered via capwap on WLC-9800-40 via Cisco switches?

The AP is connected via fiber converter (wtih PoE), Monomode fiber and directly on the sfp in the C3850 switch.

We encontred errors ans crc on switch side.

We have changed all possible elements (sfp, ethernet cables, fiber converter) and the errors are always present.

I have see in the stats of the AP that the interface wired 0 has a MTU set to 1600:

# sh int wired 0
wired0 Link encap:Ethernet HWaddr 68:49:91:E2:E3:F0
inet addr: 10.10.10.4 Bcast: 10.10.10.63 Mask: 255.255.255.192
UP BROADCAST RUNNING PROMISC MULTICAST MTU:1600 Metric:1
collisions:0 txqueuelen:80
Base address:0x7000
full Duplex, 1000 Mb/s

5 minute input rate 4092070 bits/sec, 439 packets/sec
5 minute output rate 128249 bits/sec, 63 packets/sec
Wired0 Port Statistics:
RX PKTS : 161934754/5583 TX PKTS : 161934754/5583
RX BYTES : 182465664205/6160544 TX BYTES : 182465664205/6160544
RX DROPS : 0/0

I think there is something wrong between the fiber convert and the AP, I don't know if the convert check the MTU, but the MTU between the switch (1500) and the AP (1600) seems different.

I would like to modifiy the MTU of the AP to 1500 instead of 1600, how can i do it?

I try in cli => i have don't find... I try from the WLC => i have don't find...

Can you help me to modify the MTU on the interface wired 0 of the C9166i?

I attach the stats of the corresponding switch port from the C3850.

Best regards,

Guy

[Leo Laohoo]

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@GQ_Hub1 wrote:

175069 input errors, 11730 CRC

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Post the complete output to the following commands (attached to a text file): 

sh controll e Te2/0/3
sh interface Te2/0/3 transceiver details

[GQ_Hub1]

Hello Leo,

I have attach the requested logs.

BR,

Guy

[Leo Laohoo]

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@GQ_Hub1 wrote:

1566054 SymbolErr frames         
   2078 Collision fragments      
  79748 FcsErr frames 

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That is a ton of line errors being received. 

I would get replace the patch cables first.  If the issue continues, replace the optic in the AP.

[GQ_Hub1]

Thank you for your reply.

The MTU shouldn't be the cause, nor should the copper cables.

I'll look into the fiber optic side.

[GQ_Hub1]

Hello,

I'm back about my crc problem between AP and optic converter.

I suspect a issue with the speed negociation between AP and optic converter.

The  AP has an interface that possibly goes to 2,5Gbps.

How can i set the speed to 1Gbps via the controller or cli?

I don't find the functionality...

Thanks for your help,

BR

Guy