Autonegotiation Lab Question (100-105 Simlite)

CertifiedMonkeyCertifiedMonkey Posts: 172Member ■■□□□□□□□□
I have a question about the results from an autonegotiation lab in the Simlite software included with the book.
For those of you who have the 100-105 Simlite software, this post is referring to the "Switch Interfaces and Forwarding" lab.

For those of you who don't have the software, let me explain the topology and the tasks:

Topology:
Router "R1's" Gi0/0 interface is connected to switch "SW1's" fa0/3 port.

Tasks:
Router(config-if)# duplex fullRouter(config-if)# no shutdown
The switch is using default settings.

Results and Question

The result of the lab was the switch autonegotiating to use 100 Mbps as the port speed, but the duplex is full. The explanation for the answer was that the switch had to learn the duplex with autonegotiation since R1 was configured to use full duplex. Isn't the duplex supposed to be half when 100 Mbps is used?

I did the same thing in packet tracer and the result was 100 Mbps/Half. Who's correct here?

Comments

  • clarsonclarson Posts: 897Member ■■■■□□□□□□
    did the same thing on real equipment and it is 100bps/Full

    although, i would think doing
    shutdown
    do show interface GI 0/0 to see what the duplex setting is
    duplex full to change the setting from auto
    no shut to bring the interface up

    the way you described it:
    no shut, duplex full
    the no shut brings up the interface (should be auto nego to full), then doing a duplex full. I don't know if that is going to do anything as the duplex setting is already full.
  • CertifiedMonkeyCertifiedMonkey Posts: 172Member ■■□□□□□□□□
    clarson wrote: »

    the way you described it:
    no shut, duplex full
    the no shut brings up the interface (should be auto nego to full), then doing a duplex full. I don't know if that is going to do anything as the duplex setting is already full.


    Sorry, I mistyped the commands in the wrong order in my post. It's supposed to be duplex full then no shut (which is how the simulator says to do it). Same results.
    clarson wrote: »
    did the same thing on real equipment and it is 100bps/Full

    If this is the result you got on real equipment then I will accept it as the answer. Can't really trust the simulators.
  • clarsonclarson Posts: 897Member ■■■■□□□□□□
    Sorry, I mistyped the commands in the wrong order in my post. It's supposed to be duplex full then no shut (which is how the simulator says to do it). Same results.

    it is always 100/Full for me
  • james43026james43026 Posts: 303Member
    On real equipment, you will always get the following, the 100 Mbps standard will always default to half-duplex if there is no duplex information provided in the FLPs / no FLPs. As the 100 Mbps standard is required to default to half duplex if no FLPs with duplex info is received / no FLPs are received. Again this is just the default for 100Mbps. 1000Mbps is required to default to full duplex if no FLPs with duplex information are received / no FLPs are received. And if both sides of a connection are hard coded for a specific speed, such as one side being 100 Mbps, and the other is 1000 Mbps, then the result will most likely be no link established between the devices. Speed can always be determined by the device that has parallel detection and auto negotiation enabled, by simply looking at what the bit rate is. And last, you must remember that duplex can only be determined by the use of auto-negotiation, if auto-negotiation is present on both sides, in the event that auto-negotiation for duplex is disabled on either or both sides of a connection, then the default for the speed being used is selected, assuming it hasn't been hard coded. If you want to see proof of this information, then you can refer to this cisco article, that will show you exactly what will happen under different circumstances. In which it shows the following



    Configuration NIC (Speed/Duplex)
    Configuration Switch (Speed/Duplex)
    Resulting NIC Speed/Duplex
    Resulting Catalyst Speed/Duplex
    Comments


    100 Mbps, Full-duplex
    AUTO
    100 Mbps, Full-duplex
    100 Mbps, Half-duplex
    Duplex Mismatch1




    This indicates that either the configuration on your equipment in the lab is wrong, or the lab simulator you are using doesn't function correctly. Either way, the answer that you were given in the material is incorrect. You will discover that when it comes to networking, there are lots of books, websites, and other sources that have incorrect information.
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