Hubs on a NIC (was:Re: what about 48 bits?)

Steven Bellovin smb at
Wed Apr 7 20:00:00 CDT 2010

On Apr 7, 2010, at 11:03 16AM, Joe Greco wrote:

>> On Wednesday 07 April 2010 07:18:57 am Joe Greco wrote:
>>> To me, this is a Dilbert-class engineering failure.  I would imagine that
>>> if you could implement a hub on the network card, the same chip(s) would
>>> work in an external tin can with a separate power supply.  Designing a
>>> product that actually exhibits a worse failure mode than 10base2 is ...
>>> strange to me.
>> I have in my gear museum a fairly large box with a couple of this type of 'hub 
>> on a card' installed.  And in this particular case, it made perfect sense, as 
>> the box is an Evergreen Systems CAPserver, and has 16 486 single-board 
>> computers tied to two 8-port hub cards (two ports on each modular plug, too), 
>> with....wait for it... a 10Base-2 uplink.  These were used mostly for remote 
>> network access and remote desktop access.
>> If you want more data on this old and odd box, see 
>> I can see a hub card being useful in an old NetWare server setting, though, 
>> since if the server went down you might as well not have a network in the first 
>> place, in that use case.
> Certainly.  I can come up with a bunch of reasonable-use scenarios too,
> but most of the people here will have run into that awful situation where
> a product is used in a manner that isn't "Recommended".
> In this case, I know that some of these cards were marketed in the same
> manner that workgroup hubs/switches are marketed; you would daisy-chain
> these stupid things so that your PC would feed the cubes right around you
> and then have an uplink and downlink a few cubes to the next "hub".

When I had the need to wire a building around 1987, I opted for the multiport 10Base5 repeaters that DEC made -- they were called DELUAs, I think.  I'd had quite enough of distributed single points of failure, thank you.
> Remember, it was this strange time when people were uncertain about how 
> networks were going to evolve, and what the next thing would be, and
> even then, 10baseT was being deployed over Cat3 (sometimes recycled/
> repurposed), so any sort of "enabling" gadget such as these cards had a
> tendency to be abused in various ways.

Right -- the wire and pin assignments for 10BaseT and 100BaseT were designed to permit sharing the cable between Ethernet and phone.
> Two ports on each modular plug, though.... (shudder)  ;-)

Hey, I had that in my house on my 100BaseT network, till I upgraded to gigE and had to give in and buy another switch.  (Sigh -- home network configurations of NANOGers.  I'm contemplating putting in VLANs now...)

		--Steve Bellovin,

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