High input error on interface connected to Wireless AP

[wsoonhin]

Hi,

I have a cisco 9300 multigig poe switch where I use to connect to AP. The AP model i have is 3702I, all my AP connected to the switchport have high input error as seen below:

TenGigabitEthernet1/0/10 is up, line protocol is up (connected)
Hardware is Ten Gigabit Ethernet, address is d477.98db.278a (bia d477.98db.278a)
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s, media type is 100/1000/2.5G/5G/10GBaseTX
input flow-control is on, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:13, output 00:00:00, output hang never
Last clearing of "show interface" counters 1w1d
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 67000 bits/sec, 54 packets/sec
905237 packets input, 302054885 bytes, 0 no buffer
Received 37145 broadcasts (24782 multicasts)
0 runts, 24639 giants, 0 throttles
24639 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 24782 multicast, 0 pause input
0 input packets with dribble condition detected
16007098 packets output, 2687505374 bytes, 0 underruns
Output 6185350 broadcasts (0 multicasts)
0 output errors, 0 collisions, 1 interface resets
24773 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

I have tried set the port speed to 1000, still have error.

Any idea what could be the issue here?

thanks

regards

[balaji.bandi]

is this only 1 AP issue ? or does any AP have the same issue

can you post the below information ;

show run TenGigabitEthernet1/0/10

show controller  TenGigabitEthernet1/0/10

[MHM Cisco World]

24639 giants<- this because MTU size is large than interface default.

[wsoonhin]

Hi,

It happens to all switch interfaces connected to the AP. After further investigation, the AP interface BVI1 by default has MTU of 1792.

interface BVI1
mtu 1792
ip address x.x.x.x x.x.x.x

GigabitEthernet0 is up, line protocol is up
Hardware is PowerPC Ethernet, address is 1880.905c.a548 (bia 1880.905c.a548)
MTU 1792 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full Duplex, 1Gbps, media type is T
output flow-control is unsupported, input flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/18174/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 2000 bits/sec, 3 packets/sec
5 minute output rate 1000 bits/sec, 1 packets/sec
288443 packets input, 18106520 bytes, 0 no buffer
Received 273964 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
36974 packets output, 16874806 bytes, 0 underruns
0 output errors, 0 collisions, 2 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

Below is the AP setting from the controller:

I have tried changing the MTU via CLI directly from the AP, but the value did not change.

[MHM Cisco World]

https://mrncciew.com/2013/04/07/configuring-tcp-mss/

if AP is connect to WLC.
if not what is AP model ?

[wsoonhin]

Hi,

The AP model is 3702i. Yes the AP is managed by WLC (5800 Series)

[patoberli]

Do you have set anything under Wireless -> Access Points -> Global Configuration -> Global TCP Adjust MSS?

The WLC itself doesn't allow changes to the MTU as far as I know. 

[wsoonhin]

Hi,

Below are the Wireless -> Access Points -> Global Configuration -> Global TCP Adjust MSS setting:

But I still do not understand why the AP interface BVI comes with the default MTU of 1792?

I can't change the value nor delete it via CLI.

Manually setting the TCP MSS from the WLC did not resolve the issue as well.

regards

[patoberli]

What kind of WLC do you have? Is it a converged one (running on the 9300)?

And which software release is running on it?

[wsoonhin]

Not converged.

Here is my WLC model:

The AP model is Aironet 3702I

[patoberli]

If I'm not mistaken, this software release is from 2015. You might want to upgrade, if the APs are compatible: https://www.cisco.com/c/en/us/support/wireless/5700-series-wireless-lan-controllers/products-release-notes-list.html
On this model might exist a "system mtu" command, not sure if that has any influence on the WLC portion though: https://www.cisco.com/c/en/us/td/docs/wireless/controller/5700/software/release/3e/consolidated/command-reference/b_multi_3e_5700_cr.pdf page 239.