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New Member

Forcing ports to 1G Speed

Hello,

I currently have a C3750G connected to a C3560G with default auto-negotiation settings. Ports are up and connected a-100 and a-full.

I am trying to change the ports speed to 1G, and have tried all possible combinations of "speed 1000" and "duplex full" setting on both ends to no avail.

What should port settings be for 1G speed between the two switches?

Here are the current port settings:
C3750G:

interface GigabitEthernet1/0/1

switchport trunk encapsulation dot1q

switchport trunk native vlan 10

switchport mode trunk

end

C3560G:

interface GigabitEthernet0/1

switchport trunk encapsulation dot1q

switchport trunk native vlan 10

switchport mode trunk

srr-queue bandwidth share 1 30 35 5

priority-queue out

mls qos trust cos

auto qos trust

end

Thanks for your assistance



1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: Forcing ports to 1G Speed

Hello Highmiles2,

autonegotation should work, however 1Gbps speed requires a cable with 4 working pairs.

Try to change the cable ( I suppose the ports are RJ-45 )

Hope to help

Giuseppe

8 REPLIES
Hall of Fame Super Silver

Re: Forcing ports to 1G Speed

Hello Highmiles2,

autonegotation should work, however 1Gbps speed requires a cable with 4 working pairs.

Try to change the cable ( I suppose the ports are RJ-45 )

Hope to help

Giuseppe

Forcing ports to 1G Speed

hi High,

try to issue the switchport nonegotiate on both the ports and then to set again speed 1000 and duplex full

Alessio

Cisco Employee

Forcing ports to 1G Speed

Hi Alessio,

Any need to use the switchport nonegotiate here? To my best knowledge, this command is related only to DTP and has no effect on Ethernet autonegotiation. I don't see a reason to use switchport nonegotiate in this case.

Best regards,

Peter

Re: Forcing ports to 1G Speed

Hi Peter,

This time is more matter of experience. I was in the same situation with a very similar configuration and only after disabling the trunk negotiation the link was available to be configured at the speed I wanted. according theory, Giuseppe is right and possibly even some sources of frequencies or calor can block the Ethernet cable to use the frequencies necessary to 1g. But I do believe that sometimes, to share our own experience can be very helpful even if no Cisco book would agree

Alessio

Hall of Fame Super Gold

Forcing ports to 1G Speed

autonegotation should work, however 1Gbps speed requires a cable with 4 working pairs.

I'll agree with Giuseppe's post.  For GigabitEthernet to work, make sure you run a TDR (just to make sure) that Pair D is "Normal".  If not then the link won't negotiate to 1 Gbps but either 10 Mbps (if cable length >100 metres) or 100 Mbps.

I recommend you run the TDR command from the 3750G.  Here's how you run TDR:

1.  Command:  test cable tdr interface Gi ;

2.  Wait for approximately 5 to 7 seconds;

3.  Command:  show cable tdr interface Gi ; and

4.  Post the output to #4.

WARNING:  Running the TDR may cause your link to drop for approximately 5 seconds.

speed 1000

I wouldn't use this.  Instead I'd use the command "speed AUTO 1000".

New Member

Forcing ports to 1G Speed

Hi everyone,

Switches are on seperate floors. There is a 60' CAT6 cable run extended from one floor to the other and terminates on a stand alone single RJ45 wall mount ports just couple of feets away from switches at both ends:

  1. I twice replaced the patch cables on both ends this past Tuesday, but no luck.
  2. As suggested, I applied the "switchport nonegotiate" on both ends, but that did not help either.
  3. Finally, i applied old school "Troubleshooting Basics 101" skills and moved switches directly next to each other and connected the switch via a 6 foot CAT6 cable (by-passed the extended cabling).... it worked. With default port settings, both ports auto-negotiated and connected at 1G/Full speed.

I've contacted the vendor to check internal wiring....something in the wiring allowed ports at defualt settings to connect at a-100M/a-Full but denied/blocked 1G negotiation!...

Thanks everyone for your help, I never thought it is wiring simply because ports connected at 100M/Full.

Thanks

Hall of Fame Super Gold

Forcing ports to 1G Speed

I twice replaced the patch cables on both ends this past Tuesday, but no luck.

Did you run the TDR commands on the 3750G switch?

New Member

Re: Forcing ports to 1G Speed

Any wiring I have done gets fully tested and a report comes to me to review.

It's the only way to get cabling teams to check their work.

For patch cables I might try a few cables but typically buy tested patch cables to avoid hassles in the field.

Cheers

Sent from Cisco Technical Support iPhone App

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