Link Utilization is more than 200%

[Nitzbegin]

Hi All,

The Capacity Mgmt team gave me this for investigation.

Serial No	Interface	Bandwidth	31-Oct	1-Nov	2-Nov
1	SwitchA GigabitEthernet1/0/10 (Gi1/0/10) - *** L2 Link to SwitchB Gi4/27 ***	10 MBit/s	226.5	329.6	214.7

They reported that the 10Mbps link is getting highly utilized more,. than it is use for,

When i looked into this,I suspected.

This is not due to wrong configuration on the interfaces.,but its all because of the Media connected in between them,

This is to highlight you all that, the interface is 1000BaseTX on one end and 1000BaseT on the other.

1000BaseTX ---------------------- 1000BaseT

(Fast sender)                                     (Slow receiver)--- ( Supports only Cat5 and 5e)
(Supports Cat6 but its

backward compatibile to 5 and 5e)                                          

This doesn’t affect in data transfer, and yes it may affect the reporting  (Link Utilization reporting)

Thus, the device Switch A can transmit  at higher speeds (Capacity of cat 6e – 1Gbps) and the device SwitchB only can accept the data at speed of (10 and 100Mbps(Cat5e))

To fix this we may need to either change the cable both ends or configure less speed on one end.( But configuring lower speed on trunks is not as per the Bank Standard)

SwitchA#sh inter Gi1/0/10

media type is 10/100/1000BaseTX

SwkitchB#sh inter GigabitEthernet4/27

media type is 10/100/1000BaseT 

My concern is whether was anything woring in the investigation, If it is so,, can u pls correct me, and make me understand on this issue,.

I really doubt , where the 10Mbps came into picture.,

Regards,

Nithin M

[nspasov]

Hello Nithin-

Couple of things to note:

1. Cat5e can support up to 1000Mbs

2. If the speed and duplex are not manually configured and the cables/interfaces are OK then they should negotate 1000Mbs full duplex on both ends

I am suspecting that you either have a bad cable or a bad port...most likely a bad cable but before we jump into any conclusions can you post the output from the following commands from both devices:

show interface your_interface_name_and_number 

show interface your_interface_name_and_number capabilities

show run interface your_interface_name_and_number

Thank you for rating helpful posts!

[Nitzbegin]

Hi Neno,

Please find the requested info below,;

------------------ On SwitchA ---------------------------

SwitchA#sh run inter Gi1/0/10
Building configuration...

Current configuration : 385 bytes
!
interface GigabitEthernet1/0/10
 description *** L2 Link to SwitchB Gi4/27 ***
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 311,327,337,621-623,628,636,644,645,660
 switchport mode trunk
 logging event link-status
 logging event trunk-status
 logging event bundle-status
 load-interval 30
 mls qos trust dscp
 channel-group 32 mode desirable non-silent
end

SwitchA#

SwitchA#sh inter Gi1/0/10
GigabitEthernet1/0/10 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 0008.2fb4.298a (bia 0008.2fb4.298a)
  Description: *** L2 Link to SwitchB Gi4/27 ***
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 6/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/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 00:00:04, output 00:00:08, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 643
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  30 second input rate 27294000 bits/sec, 3255 packets/sec
  30 second output rate 1864000 bits/sec, 880 packets/sec
     5992231691 packets input, 6721805032454 bytes, 0 no buffer
     Received 17401573 broadcasts (16530427 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 16530427 multicast, 0 pause input
     0 input packets with dribble condition detected
     1679810027 packets output, 458818530453 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
SwitchA#

SwitchA#sh inter Gi1/0/10 capabilities
GigabitEthernet1/0/10
  Model:                 WS-C3750X-48
  Type:                  10/100/1000BaseTX
  Speed:                 10,100,1000,10000,auto
  Duplex:                half,full,auto
  Trunk encap. type:     802.1Q,ISL
  Trunk mode:            on,off,desirable,nonegotiate
  Channel:               yes
  Broadcast suppression: percentage(0-100)
  Flowcontrol:           rx-(off,on,desired),tx-(none)
  Fast Start:            yes
  QoS scheduling:        rx-(not configurable on per port basis),
                         tx-(4q3t) (3t: Two configurable values and one fixed.)
  CoS rewrite:           yes
  ToS rewrite:           yes
  UDLD:                  yes
  Inline power:          no
  SPAN:                  source/destination
  PortSecure:            yes
  Dot1x:                 yes
SwitchA#

_--------------------------- On Switch B------------------

SwitchB#sh run inter Gi4/27
Building configuration...

Current configuration : 397 bytes
!
interface GigabitEthernet4/27
 description *** L2 Link to SwitchA Gi1/0/10 ***
 switchport
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 311,327,337,621-623,628,636,644,645,660
 switchport mode trunk
 logging event link-status
 logging event trunk-status
 logging event bundle-status
 load-interval 30
 mls qos trust dscp
 channel-group 31 mode desirable non-silent
end

SwitchB#sh inter Gi4/27
GigabitEthernet4/27 is up, line protocol is up (connected)
  Hardware is C6k 1000Mb 802.3, address is f0f7.5569.b7ca (bia f0f7.5569.b7ca)
  Description: *** L2 Link to SwitchA Gi1/0/10 ***
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 5/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is 10/100/1000BaseT
  input flow-control is off, output flow-control is off
  Clock mode is auto
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:05, output 00:00:45, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 8978
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  30 second input rate 1566000 bits/sec, 868 packets/sec
  30 second output rate 20217000 bits/sec, 2335 packets/sec
     1681941296 packets input, 459048513180 bytes, 0 no buffer
     Received 103188681 broadcasts (100048440 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
     0 input packets with dribble condition detected
     5993142175 packets output, 6722715378717 bytes, 0 underruns
     0 output errors, 0 collisions, 4 interface resets
     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

SwitchB#sh inter Gi4/27 capabilities
GigabitEthernet4/27
  Model:                 WS-X6748-GE-TX
  Type:                  10/100/1000BaseT
  Speed:                 10,100,1000,auto
  Duplex:                half,full
  Trunk encap. type:     802.1Q,ISL
  Trunk mode:            on,off,desirable,nonegotiate
  Channel:               yes
  Broadcast suppression: percentage(0-100)
  Flowcontrol:           rx-(off,on,desired),tx-(off,on,desired)
  Membership:            static
  Fast Start:            yes
  QOS scheduling:        rx-(2q8t), tx-(1p3q8t)
  QOS queueing mode:     rx-(cos), tx-(cos)
  CoS rewrite:           yes
  ToS rewrite:           yes
  Inline power:          no
  Inline power policing: no
  SPAN:                  source/destination
  UDLD                   yes
  Link Debounce:         yes
  Link Debounce Time:    no
  Ports-in-ASIC (Sub-port ASIC) : 25-48 (25-36)
  Remote switch uplink:  no
  Dot1x:                 no
  Port-Security:         yes
SwitchB#

[nspasov · Accepted solution]

So based on the output, both links are running in full-duplex and speed of 1000Mbs. So it appears that your connection is good. 

Now looking back at:

The title:

Link Utilization is more than 200%

And part of the problem description:

They reported that the 10Mbps link is getting highly utilized more,. than it is use for,

I have the feeling that perhaps your management software is not properly configured. Is it possible that your management software is configured with the wrong interface bandwidth? For instance, it is configured that those interfaces only have 10Mb or 100Mb while they actually have 1000Mb?

Thank you for rating helpful posts!

[Nitzbegin]

Yes, I do suspect the same , the same would have happened,

Can u confirm me, if they would have used 10BaseT OID to poll this information.

Coz i got confused , that Cat 5 supports (10Mbps) and was suspecting Cat5 cable might be used for trunks.

Can u clarify me on this,

Thanks,

Nithin

[nspasov]

Based on this output:

Full-duplex, 1000Mb/s,

we can tell that the interfaces were successfully able to negotiate and run 1000Mbs at full-duplex. If there was an issue here you would see one side at 100Mb and the other at 10Mb with half-duplex or some other variation. So I would definitely check the settings on the monitoring software.

Cat5 can do 10/100Mb

Cat5e can do 10/100/1000Mb

Cat6 can do 10/100/1000/10000Mb (at short distance)

Thank you for rating helpful posts!

[Nitzbegin]

Thanks Neno,

It was very useful to me,

Nithin,