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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. – Joey Miller Aug 5 '16 at 7:18
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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.

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  • 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. – Bill Brower 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. – Ronnie Royston 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). – Karl Billington Aug 5 '16 at 15:17
  • True. Yes, I meant bandwidth command. – Ronnie Royston Aug 5 '16 at 17:34

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