Is "Too large frames" a problem ?

[Fabri_Fabri]

Some colleagues notified me that RDP connection they are using hiccups. Windows draw after a second and so on.

Those colleagues are in a branch office connected to a 2960s that is also connected to a 2960 located in headquarter office via dedicated link, using TRUNK.

Both uplink trunk switches are forced to 100Mb full duplex because of layer1 appliance of the provider.

Investigating a bit using "sh controllers ethernet-controller" turns out that uplink trunk interfaces of both switches report a lot of "Too large frames".

MTU size of 2960 is 1500.

QoS is disabled.

CPU seems ok (40/60)

Can you please help me to diagnose and fix this behavior ?

Thanks for help.

[Madhukrishnan Gopinathan Nair]

Please share 

sh int <>

sh int <> counters errors

Thanks,

Madhu

[Madhukrishnan Gopinathan Nair]

Are both sides MTU 1500?

[Fabri_Fabri]

Both 2960 are MTU 1500.

Don't know the SDH layer 1 MTU size appliance though.

[Madhukrishnan Gopinathan Nair]

Is the output drops increasing continually? Configure Load interval on the interface to 30 sec so that we can have a much better view of how much traffic traversing over it.

[Madhukrishnan Gopinathan Nair]

Also is it possible to increase the MTU on both sides just to check if that solves this problem?

Thanks,

Madhu

[Madhukrishnan Gopinathan Nair]

Since it is 2960 you have to apply system mtu jumbo globally and requires a reload. 

Thanks,

Madhu

[Fabri_Fabri]

Will enabling jumbo mtu disrupt something ?

Is it a safe fix ?

Thanks !!!

[Fabri_Fabri]

Hi,

is it load-interval 3 30 ? or load-interval 1 30 ?

[Fabri_Fabri]

This is the HQ uplink interface:
 

switch48-04#sh interfaces gigabitEthernet 1/0/43
GigabitEthernet1/0/43 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is b4e9.b099.352b (bia b4e9.b099.352b)
  Description: TRUNK
  MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
     reliability 255/255, txload 5/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input never, output 00:00:00, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 22653480
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 388000 bits/sec, 303 packets/sec
  5 minute output rate 1977000 bits/sec, 660 packets/sec
     415966026 packets input, 149124634477 bytes, 0 no buffer
     Received 7321375 broadcasts (5696260 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 5696260 multicast, 0 pause input
     0 input packets with dribble condition detected
     1018735876 packets output, 604726049775 bytes, 0 underruns
     0 output errors, 0 collisions, 1 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
    
    
Port        Align-Err     FCS-Err    Xmit-Err     Rcv-Err  UnderSize  OutDiscards
Gi1/0/43            0           0           0           0          0     22653480

Port      Single-Col  Multi-Col   Late-Col  Excess-Col  Carri-Sen      Runts     Giants
Gi1/0/43           0          0          0           0          0          0          0

And this is the branch office uplink interface:
 

switch48-07#sh int gigabitEthernet 1/0/48
GigabitEthernet1/0/48 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is ece1.a9ae.08b0 (bia ece1.a9ae.08b0)
  Description: TRUNK
  MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 7/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input never, output 00:00:00, output hang never
  Last clearing of "show interface" counters 00:54:35
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 3132000 bits/sec, 1204 packets/sec
  5 minute output rate 426000 bits/sec, 353 packets/sec
     1874124 packets input, 866594668 bytes, 0 no buffer
     Received 264680 broadcasts (229880 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 229880 multicast, 0 pause input
     0 input packets with dribble condition detected
     1115200 packets output, 189351650 bytes, 0 underruns
     0 output errors, 0 collisions, 0 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
    
Port        Align-Err     FCS-Err    Xmit-Err     Rcv-Err  UnderSize  OutDiscards
Gi1/0/48            0           0           0           0          0            0

Port      Single-Col  Multi-Col   Late-Col  Excess-Col  Carri-Sen      Runts     Giants
Gi1/0/48           0          0          0           0          0          0          0

Please note that reset counter on Gi1/0/48 interface to see errors increase.

[Madhukrishnan Gopinathan Nair]

The interface 1/0/43 shows lot of output drops.

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 22653480

Can you please check the interface utilization graph to see you are not oversubscribing it.

Thanks,

Madhu

[Fabri_Fabri]

That interface is the uplink trunk to other office.

Where can I check the utilization graph and hwo to understand if oversubscribing it ?

[Fabri_Fabri]

I browsed switch via http and did this shot. Frames seem too big.