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New Member

port speed and duplex

If i set a port to 100 and full duplex on a Cisco 4003 switch. What would happen if i had a pc's nic card set to half duplex or 10mb, would it connect to the network? Would the switch go back to half or 10mb?

Thanks,

James

1 ACCEPTED SOLUTION

Accepted Solutions

Re: port speed and duplex

NO, if switc port is 100-full and PC is 10-half, it won't work, you'll see "notconnect" (for Catalysts) or "down/down" (for IOS switches). In case of speed mismatch ethernet doesn't work. In case of duplex mismatch (e.g. 100full---100half) it'll work with degraded performance. On full-duplex side you'll see "CRC errors" and on the half-duplex side you'll see "late collisions".

Regards.

3 REPLIES
VIP Purple

Re: port speed and duplex

Hello,

the switch will only adapt to whatever your PC´s NIC is set to if you have the speed set to auto:

interface FastEthernet0/1

speed auto

Keep in mind that if the speed is set to auto, you will not be able to set duplex.

If you hard-code the speed and duplex settings, you will have a duplex mismatch:

interface FastEthernet0/1

speed 100

duplex full

Keep in mind that if the speed is set to 10 or 100, and you do not configure the duplex setting, the duplex mode is set to half.

HTH,

Georg

New Member

Re: port speed and duplex

Georg,

If i hard-code the speed and duplex to 100 and full, what would happen to the PC if the PC is hard-code at 10 and half duplex? Would the PC still connect at 10?

Thanks,

James

Re: port speed and duplex

NO, if switc port is 100-full and PC is 10-half, it won't work, you'll see "notconnect" (for Catalysts) or "down/down" (for IOS switches). In case of speed mismatch ethernet doesn't work. In case of duplex mismatch (e.g. 100full---100half) it'll work with degraded performance. On full-duplex side you'll see "CRC errors" and on the half-duplex side you'll see "late collisions".

Regards.

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