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Full and half duplex.

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  • Ethernet Card
  • Networking
Last response: in Networking
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Anonymous
August 9, 2004 1:34:45 AM

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?

More about : full half duplex

Anonymous
August 9, 2004 8:39:39 AM

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
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August 23, 2004 8:16:08 AM

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?
>
>
>
!