What is the default speed of a Fast Ethernet Interface of Cisco 2900 Switch that was just reset to default settings using write erase?

I'm asking because my Wireshark capture of ARP packets gives a much reduced speed of 1914 KB.

2 Answers 2


The default speed and duplex of a Cisco 29xx fast ethernet switch interface which was reset to default settings would be Auto.

ARP frames are really no way to measure an interface speed. An ARP request receives an ARP reply. You cannot measure the interface speed from that.

One problem could be that one side of the link is set to Auto, but the other side is set to a fixed speed and/or duplex. That will cause serious problems on the link, and it could look like your link speed is very slow. You will get a lot of interface errors and that will cause re-transmissions.

See this Cisco table for the combinations which can cause duplex mismatches.


Speed is set to auto when out of the box, If I recall correctly Those you generally get a combination of 24 or 48 10/100/1000 ports along with either one or two 1 GB or 10 GB SFP slots which I would use ass trunk ports. Those are the "max speeds hardware rating wise" as far as the bandwidth you pass through interfaces....that has a lot of factors including network environment number of hosts, protocol, bandwidth of the links connecting the ports with downstream and upstream devices....you get the point. Hardware ratings are one thing true throughout another.

  • Hey that's what I wanted to know. The exact value. Is it 10, 100 or 1000 by default? Commented Sep 20, 2016 at 11:42
  • Autosensing based on the other side of the link, speed is negotiated based on the two devices capabilities.. Although it can be adjusted manually.
    – Ty Smith
    Commented Sep 20, 2016 at 15:29

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