Guidance Required on Duplex Mismatch

Unanswered Question
Mar 11th, 2008

Dear All,

Facing issues to bring the link between FastEthernet and Gigabitethernet interfaces. Both interfaces are connected back-toback by Cat-5 crossover cable.

1. Fastethernet port - 100Mb/Full

GigabitEthernet port - 100Mb/Full

Link status :- Down

2. FastEthernet port - 100mb/Full

GigabitEthernet port - 100Mb/auto

Link Status :- Interface is UP, gigabit is receiving half-duplex.

3.FastEthernet port - 100Mb/auto

GigabitEthernet port - 100Mb/auto

Link status :- Interfaces are up and gigabit interface is getting FULL Duplex.

ACCESS-SWITCH-1>sh int fa0/3

FastEthernet0/3 is down, line protocol is down (notconnect)

Hardware is Fast Ethernet, address is 0016.9dca.bb03 (bia 0016.9dca.bb03)

Description: ## TEST CIRCUIT ##

MTU 1546 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Auto-duplex, 100Mb/s, media type is 10/100BaseTX

input flow-control is off, output flow-control is unsupported

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:01:03, output 00:00:52, 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 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

115801 packets input, 14634892 bytes, 0 no buffer

Received 9563 broadcasts (0 multicasts)

0 runts, 0 giants, 0 throttles

93 input errors, 93 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 8358 multicast, 0 pause input

0 input packets with dribble condition detected

120922 packets output, 30140304 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

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 4 (1 ratings)
Loading.
royalblues Tue, 03/11/2008 - 06:27

I would suggest using the auto option on both sides

With one side as auto, you will always end up with half duplex cos thats the way ethernet works

Hard coding both sides should have worked but i too have experienced the same problem you have mentioned with some models (both were Cisco:-)

HTH

Narayan

gaurav_thapar79 Tue, 03/11/2008 - 06:43

Hi naryanan,

Appreciate your feedback but my global customer do not want a hit-n-trial. They want everything to be hardcoded to avoid any performance issues on application level in future.

Kevin Dorrell Tue, 03/11/2008 - 08:05

There is an issue with hardcoding on a 100 <--> Gig link. The issue is that because you have disabled the autonegotiation, you have also disabled the feature of Gig (and some 100 interfaces)that it can automatically detect the cable type ... crossed or straight. In fact, in Gig, there is no such thing as a crossed cable, while in 100 there is sometimes auto-detect.

For this reason, Gig <--> 100 forced plus 100-type crossed cable is just one combination that very often does not work.

Did you hardcode the Gig side to speed 100 too?

You might find that with a straight cable, the hardcoded would work.

vaisharm Tue, 03/11/2008 - 07:08

Hi Gaurav,

Please provide the following details:

FastEthernet - Device/IOS version ?

GigabitEthernet - Device/IOS version ?

Do you have RJ-45 or SFP(i.e. Fibre) port on the GigabitEthernet end?

~Vaibhav

gaurav_thapar79 Tue, 03/11/2008 - 07:40

Hi Vaibhav,

PFA attached snapshots taken from switches.

1. FastEthernet port switch --connected to-- Gigabitport of Cisco 3825 series router.

Cisco 3550 switch details:-

Cisco IOS Software, C3550 Software (C3550-IPBASEK9-M), Version 12.2(35)SE5, RELE

ASE SOFTWARE (fc1)

Copyright (c) 1986-2007 by Cisco Systems, Inc.

"flash:c3550-ipbasek9-mz.122-35.SE5.bin"

Cisco 3825 Router details:-

VERSION 12.4.2T1 advanced ip services.

gaurav_thapar79 Tue, 03/11/2008 - 07:40

Hi Vaibhav,

PFA attached snapshots taken from switches.We are using electrical interfaces n not SFP.

1. FastEthernet port switch --connected to-- Gigabitport of Cisco 3825 series router.

Cisco 3550 switch details:-

Cisco IOS Software, C3550 Software (C3550-IPBASEK9-M), Version 12.2(35)SE5, RELE

ASE SOFTWARE (fc1)

Copyright (c) 1986-2007 by Cisco Systems, Inc.

"flash:c3550-ipbasek9-mz.122-35.SE5.bin"

Cisco 3825 Router details:-

VERSION 12.4.2T1 advanced ip services.

Actions

This Discussion