Full and half duplex.

Archived from groups: comp.dcom.lans.ethernet (More info?)

What exactly will happen if a port configured for full duplex only tries to
talk to one capable of half duplex only?

I tried taking a HP Procurve switch, connected a full duplex uplink from the
100Mb. port to the rest of my network, configured one of the 10 Mb. ports to
full duplex, and connected it to a port on a Netgear 10Mb. hub, obviously
half duplex. I then connected another port on the hub to a PC, and tried to
access the network through this mismatched connection. Sometimes I seemed
to get a reasonable connection, sometimes a very slow transfer, sometimes
the liink light would come and go, and once the whole Procurve locked up, I
couldn't get a link to anything, and I had to re-boot it. That surprised me
somewhat. What exactly was happening? Why did the results vary, And would
the problems have got worse if I had connected more devices to the hub?
2 answers Last reply
More about full half duplex
  1. Archived from groups: comp.dcom.lans.ethernet (More info?)

    In article <41168e5b$0$15849$cc9e4d1f@news.dial.pipex.com>,
    furles@mail.croydon.ac.uk says...
    > What exactly will happen if a port configured for full duplex only tries to
    > talk to one capable of half duplex only?
    >
    > I tried taking a HP Procurve switch, connected a full duplex uplink from the
    > 100Mb. port to the rest of my network, configured one of the 10 Mb. ports to
    > full duplex, and connected it to a port on a Netgear 10Mb. hub, obviously
    > half duplex. I then connected another port on the hub to a PC, and tried to
    > access the network through this mismatched connection. Sometimes I seemed
    > to get a reasonable connection, sometimes a very slow transfer, sometimes
    > the liink light would come and go, and once the whole Procurve locked up, I
    > couldn't get a link to anything, and I had to re-boot it. That surprised me
    > somewhat. What exactly was happening? Why did the results vary, And would
    > the problems have got worse if I had connected more devices to the hub?


    One follows the CSMA/CD rule and the other does not. As a result, the
    FD side constantly stomps on the transmission of the HD side *OUTSIDE*
    of its collision detect window. This kills throughput.


    --

    hsb

    "Somehow I imagined this experience would be more rewarding" Calvin
    *************** USE ROT13 TO SEE MY EMAIL ADDRESS ****************
    ********************************************************************
    Due to the volume of email that I receive, I may not not be able to
    reply to emails sent to my account. Please post a followup instead.
    ********************************************************************
  2. Archived from groups: comp.dcom.lans.ethernet (More info?)

    You will get lots of errors due to the duplex mismatch and a slow
    connection.

    "Stephen Furley" <furles@mail.croydon.ac.uk> wrote in message
    news:41168e5b$0$15849$cc9e4d1f@news.dial.pipex.com...
    > What exactly will happen if a port configured for full duplex only tries
    to
    > talk to one capable of half duplex only?
    >
    > I tried taking a HP Procurve switch, connected a full duplex uplink from
    the
    > 100Mb. port to the rest of my network, configured one of the 10 Mb. ports
    to
    > full duplex, and connected it to a port on a Netgear 10Mb. hub, obviously
    > half duplex. I then connected another port on the hub to a PC, and tried
    to
    > access the network through this mismatched connection. Sometimes I seemed
    > to get a reasonable connection, sometimes a very slow transfer, sometimes
    > the liink light would come and go, and once the whole Procurve locked up,
    I
    > couldn't get a link to anything, and I had to re-boot it. That surprised
    me
    > somewhat. What exactly was happening? Why did the results vary, And
    would
    > the problems have got worse if I had connected more devices to the hub?
    >
    >
    >
Ask a new question

Read More

Ethernet Card Networking