Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
New Member

SPEED/DUPLEX auto

Hi

what is the best config to ports on the Cisco Switch regarding Duplex & Speed;is auto config to both of them?OKK?

10XS

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Blue

Re: SPEED/DUPLEX auto

Hi Ali

The answer is it depends. If you are connecting servers and clients then as long as they are also set to auto neogitiate you should be fine.

Where i work we leave clients on auto-negotiation, any servers that are a 100full capable we set to 100full on the switch and gigabit server connectikns should be left at auto.

I have seen many problems with incorrect speed/duplex settings. The key thing is to make sure that the network people who set up the switches and the server/desktop people are all communicating.

Between switches you cause auto.

HTH

Jon

6 REPLIES

Re: SPEED/DUPLEX auto

HI Ali

It will be fine if u r having auto at both the ends.

Thanks

Mahmood

New Member

Re: SPEED/DUPLEX auto

hi Mahmoud!

what about if these ports its conected to workstation>how come?

10xs

Hall of Fame Super Blue

Re: SPEED/DUPLEX auto

Hi Ali

The answer is it depends. If you are connecting servers and clients then as long as they are also set to auto neogitiate you should be fine.

Where i work we leave clients on auto-negotiation, any servers that are a 100full capable we set to 100full on the switch and gigabit server connectikns should be left at auto.

I have seen many problems with incorrect speed/duplex settings. The key thing is to make sure that the network people who set up the switches and the server/desktop people are all communicating.

Between switches you cause auto.

HTH

Jon

New Member

Re: SPEED/DUPLEX auto

Hi Jon/Hi Mahmood!

Thanks a lot for ur reply specialy in this off days

Regards

Re: SPEED/DUPLEX auto

Hi Ali,

I Just have one comment to add:

If a switch port is configured with 100Mbps and Full Duplex (auto-negotiation is disabled -> no FLPs are sent), but the Workstation's NIC is configured for auto-negotiation --> Without auto-negotiation on the switch, FLPs (Fast Link Pulses) will not be sent to the workstation, and as a result, the workstation will configure itself to half-duplex (FLP was used to negotiate both speed and duplex), which can result in Duplex mismatch.

Switches detect duplex settings through auto-negotiation only. If both ends have auto-negotiation enabled, the duplex is negotiated. However, if either device on the cable disables auto-negotiation, the devices without a configured duplex setting must assume a default. Cisco switches use a default duplex setting of half duplex (HDX) (for 10-Mbps and 100-Mbps interfaces) or full duplex (FDX) (for 1000-Mbps interfaces -> Always Full can't be Half).

Duplex mismatch is a situation in which the switch is operating at full-duplex and the connected device is operating at half-duplex, or the other way around. The result of a duplex mismatch is extremely slow performance, intermittent connectivity, and loss of connection.

NOTE: If auto-negotiation is disabled on either end of the cable, the switch detects the speed anyway based on the incoming electrical signal.

Accordingly this is a thing that you need to consider in your network --> Either to make both sides Auto, or configure both sides explicitly to avoid any Duplex mismatch problems.

HTH and best regards,

Mohammed Mahmoud.

New Member

Re: SPEED/DUPLEX auto

Another adding if i may...

If the switches ar config for auto a trunk won't be negotiated cause both switches are waiting for the ohter to start the negotiation...

I have also had an issue that i had to config my router which only had 10 mb interfaces like this...

on the routers - duplex full

on the switches - speed 10 and duplex on auto

ciao flash

970
Views
5
Helpful
6
Replies
CreatePlease to create content