What does it mean saying the speed of a switch port (or router port)? In other word, does this mean that switch ports have a default-factory speed limit in some sense?

Thank you

  • Both ends of a link need the same speed setting to work properly.
    – MarkH
    Aug 5 '16 at 3:14
  • By default they're setup to auto-negotiate speed. But you can manually set the speed according to your demand. Aug 5 '16 at 7:18

Switch ports normally can pass traffic at 10Mbps, 100Mbps or 1000Mbps. The default is for the switch port to auto-configure its speed based on signaling between the port and the connected device.

Sometimes auto-speed doesn't work that well and then, if possible, one could manually set the speed of a port (routers, too) with the "speed" or "set speed" command.

The vast majority of switches do not support speeds over 1000Mbps, there are very high-end (think major ISP or large datacenter equipment) switches that can to 10GbPS or 40GbPS now, too.

  • Thank you Bill. Suppose an ethernet cable with 10Mbps is used, does it mean that the speed of switch port should NOT exceed this ethernet cable's speed?
    – Alli
    Aug 4 '16 at 19:43
  • That would be about a 20 year old cable. Any CAT 5 or 5e, CAT 6 or 6e cable will prove sufficient for 50Mb or 100Mb service from your provider. Aug 4 '16 at 19:45
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    If you are speaking of Cisco IOS, the speed command under interface configuration mode is only used for calculating QoS, routing protocol metrics, etc. Aug 4 '16 at 21:20
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    @RonRoyston, don't you mean the bandwidth command? The bandwidth command is used for QOS and routing metrics. The speed command does set the physical interface speed (which is actually the interface bandwidth). Aug 5 '16 at 15:17
  • True. Yes, I meant bandwidth command. Aug 5 '16 at 17:34

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