I found that different interfaces have different behaviour on different device (router, switch) when no cable is attached on Packet Tracer

Router's serial : down down

Router's ethernet: up down

Switch's : down down

What is that so special for ethernet? For serial, I was informed that the status will be up down if a cable is attached but has some mismatch for L2 configuration.

Note: I don't know if the behaviour is same if a cable is attached on the interface but the other end of the cable is not attached to any device.

  • 1
    Please consider buying a real router from ebay instead of playing with the toy sometimes known as packet tracer Jul 6, 2014 at 8:55
  • @mike So, does what Packet Tracer present invalid?
    – Ron Vince
    Jul 6, 2014 at 9:43
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    @RonVince Packet Tracer is incredibly limited. If you don't use (or want to use) real hardware, at least consider GNS3.
    – Ryan Foley
    Jul 6, 2014 at 10:41
  • @RyanFoley The problem with GNS3 is there is no switch. In PT, I can use dedicated switch instead of switching module. That's why I use PT. The router's ethernet behaviour that I have provided stands for both original ethernet interface and switching module on PT. I hope at least PT is reliable enough to check about this. The reason I ask here is to have verification about this.
    – Ron Vince
    Jul 6, 2014 at 11:04
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    Packet tracer is a cisco tool for doing labs in their network academy CCNA courses. It is NOT intended as a replacement for real gear/GNS3/IOU or other virtual labs. It does not support all the features even for CCNP level classes. Use it with configuration problems/labs at the CCNA level and it will work for you, outside of that use case expect odd behavior.
    – fredpbaker
    Jul 6, 2014 at 18:03

1 Answer 1


All the PT-jabbing aside, this is just a strange Packet Tracer behavior and does not match the real world. On a real switch, an unplugged ethernet, fast ethernet, or gigabit ethernet interface would show down down.

  • So, it is same for switch. How about router?
    – Ron Vince
    Jul 7, 2014 at 5:42
  • 1
    The same. As long as nothing is physically connected to an Ethernet port on a router, the interface should show down down. Jul 7, 2014 at 11:05
  • Ok. So, the behaviour of ethernet interface in regards to cable not connected to it is same with serial interface.
    – Ron Vince
    Jul 7, 2014 at 11:13
  • Should be, yes. I've heard of people experiencing strange behavior on ethernet ports where the port showed as up/down without having a cable plugged in, but I've never seen it, nor do I know it to be standard behavior. Jul 7, 2014 at 15:34

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