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DUPLEX MISMATCH

Good morning, i'm having a problem in my network.

it regards duplex mismatch. this is what i find in the logging.

CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet0/2 (not half duplex), with L2_HWS-3 GigabitEthernet0/1 (half duplex)

CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet0/1 (not full duplex), with L2_TOC-2 GigabitEthernet0/2 (full duplex)

when i log in into the L2_HWS-3 and try to put the speed settings manualy there is no option for this, and i dont want to change the interface of the switch that is with the full duplex to half duplex. i just want to fix the problem.

interface GigabitEthernet0/1

switchport mode trunk

end

Motherboard assembly number     : 73-12601-05
Power supply part number        : 341-0097-03
Motherboard serial number       : FOC14461A63
Power supply serial number      : DCA144581K3
Model revision number           : F0
Motherboard revision number     : A0
Model number                    : WS-C2960-24TC-S
System serial number            : FOC1446V0NA
Top Assembly Part Number        : 800-32798-01
Top Assembly Revision Number    : E0
Version ID                      : V06
CLEI Code Number                : COMSH00ARD
Hardware Board Revision Number  : 0x0A


Switch Ports Model              SW Version            SW Image                
------ ----- -----              ----------            ----------              
*    1 26    WS-C2960-24TC-S    12.2(50)SE4           C2960-LANLITEK9-M 

this is the switch that has the interface on half duplex

Motherboard assembly number     : 73-11883-06
Power supply part number        : 341-0097-03
Motherboard serial number       : FOC14331KM1
Power supply serial number      : DCA1428844A
Model revision number           : C0
Motherboard revision number     : A0
Model number                    : WS-C2960-48TT-S
System serial number            : FOC1433V2VY
Top Assembly Part Number        : 800-30858-03
Top Assembly Revision Number    : B0
Version ID                      : V03
CLEI Code Number                : COMC300ARA
Hardware Board Revision Number  : 0x02


Switch Ports Model              SW Version            SW Image                
------ ----- -----              ----------            ----------              
*    1 50    WS-C2960-48TT-S    12.2(46)SE            C2960-LANLITEK9-M      

interface GigabitEthernet0/2
switchport mode trunk
end

this is the switch with the interface on full duplex.

does someone have a idea how to fix this or how this can happen

1 Accepted Solution

Accepted Solutions

InayathUlla Sharieff
Cisco Employee
Cisco Employee

Hi Michael,

I suggest you change config to “ duplex full” on two side.

Int G0/1

(config-if)#duplex full

config t#int g0/2

(config-if)#duplex full

https://docs.google.com/viewer?a=v&q=cache:jD61goavrNMJ:www.cisco.com/en/US/docs/wireless/mwr_2941_dc/software_config/guide/3_3/ge_ifcs.pdf+duplex+settings+on+gigabitethernet0&hl=en&gl=in&pid=bl&srcid=ADGEESiObHD4cjkcGJNlzZqYW0I5ALdgZ9OTMN3K7llrGsiP2...

If you are not able to configure this provide us the output which you see under the interface?

If in case you dont want to see these messages poping up then go to the interface and disable the cdp.

HTH

REgards

Inayath

View solution in original post

6 Replies 6

blau grana
Level 7
Level 7

Hello Michael,

Can you verify that both interfaces are configured to autonegotiation?

Can you provide these command outputs?

L2_HWS-3# sh int Gi0/1

L2_HWS-3# sh run int Gi0/1

L2_TOC-2# sh int Gi0/2

L2_TOC-2# sh run int Gi0/2

Best Regards

Please rate all helpful posts and close solved questions

Best Regards Please rate all helpful posts and close solved questions

InayathUlla Sharieff
Cisco Employee
Cisco Employee

Hi Michael,

I suggest you change config to “ duplex full” on two side.

Int G0/1

(config-if)#duplex full

config t#int g0/2

(config-if)#duplex full

https://docs.google.com/viewer?a=v&q=cache:jD61goavrNMJ:www.cisco.com/en/US/docs/wireless/mwr_2941_dc/software_config/guide/3_3/ge_ifcs.pdf+duplex+settings+on+gigabitethernet0&hl=en&gl=in&pid=bl&srcid=ADGEESiObHD4cjkcGJNlzZqYW0I5ALdgZ9OTMN3K7llrGsiP2...

If you are not able to configure this provide us the output which you see under the interface?

If in case you dont want to see these messages poping up then go to the interface and disable the cdp.

HTH

REgards

Inayath

Yes for sure i can!

L2_TOC-2#sh int gi0/2
GigabitEthernet0/2 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 68bd.ab06.7732 (bia 68bd.ab06.7732)
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 5/255, rxload 4/255
  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 00:00:23, 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: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 1818000 bits/sec, 793 packets/sec
  5 minute output rate 2312000 bits/sec, 855 packets/sec
     5437051048 packets input, 804345010799 bytes, 0 no buffer
     Received 505407723 broadcasts (500396623 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 500396623 multicast, 0 pause input
     0 input packets with dribble condition detected
     298398255 packets output, 131283931913 bytes, 0 underruns
     0 output errors, 0 collisions, 1 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
 
  L2_TOC-2#sh run int gi0/2
Building configuration...

Current configuration : 59 bytes
!
interface GigabitEthernet0/2
switchport mode trunk
end

-----------------------------------------------------------------------------------------------
L2_HWS-3#sh int gi0/1
GigabitEthernet0/1 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 0817.354a.1a99 (bia 0817.354a.1a99)
  Description: [* L2_SMD-1 *]
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 4/255, rxload 5/255
  Encapsulation ARPA, loopback not set
  Keepalive not set
  Half-duplex, 100Mb/s, link type is auto, 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 00:00:00, output 00:00:22, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 19122914
  Queueing strategy: fifo
  Output queue: 0/0 (size/max)
  5 minute input rate 2333000 bits/sec, 878 packets/sec
  5 minute output rate 1883000 bits/sec, 816 packets/sec
     8539156 packets input, 3694453862 bytes, 0 no buffer
     Received 578202 broadcasts (307270 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 307270 multicast, 0 pause input
     0 input packets with dribble condition detected
     31168792 packets output, 7415380699 bytes, 0 underruns
     0 output errors, 470221 collisions, 1 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
L2_HWS-3#


L2_HWS-3#sh run int gi0/1
Building configuration...

Current configuration : 96 bytes
!
interface GigabitEthernet0/1
description *** uplink L2_TOC-2 ***
switchport mode trunk
end

L2_HWS-3#

if you need more info let me know
thanks!!!!

i can only set the full duplex settings on one of the two switches. only on the L2_TOC-2 the other switch dont have the option of speed ore duplex settings on the interface.

i know i can turn it off but i just want it to work with out this log entry.

it has to function normal so something is not correct.

Thanks!

Both ports are gigabit ports, but speed is only 100Mb/s. Can you verify that cable which connects both switches is able to support 1000Mb/s?

Also I read that sometimes you have to configure media-type on interface and than you can configure duplex and speed under interface.

Best Regards

Please rate all helpful posts and close solved questions

Best Regards Please rate all helpful posts and close solved questions

"

Also I read that sometimes you have to configure media-type on interface and than you can configure duplex and speed under interface. "

this fixed the problem, both are now on full duplex speed 100.

the cable i could not check, the racks are high in a factory hall, put i presume that they will not be capable of running 1gb.

but i'm happy anyway.

Thanks allot

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