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Back when I was just getting into networking, ethernet hubs were common, and switches were a fancy, expensive alternative. Then the price of switches came down so much that hubs became pretty much obsolete, except when you actually didn't want switching - as wikipedia points out, "hubs can still be useful in certain circumstances," such as "for inserting a protocol analyzer into a network connection." That's a particular use case I've come across several times, especially at work -- I haven't yet learned all the ins and outs of configuring RSPAN (Cisco's implementation of port mirroring) on Cisco switches, and sometimes it'd really just be easier to plug a laptop into a hub with the system I want to monitor.

The only problem is, I can't actually find any place to buy a hub. Small switches start at $25, so I'd expect to be able to find a hub even cheaper... except I can't actually find one at all. A google product search for "ethernet hub" instead finds ethernet switches and usb hubs instead, plus a few expensive ethernet devices that I'm not quite sure what they are :)

Does anybody actually make hubs anymore? Or am I going to have to hang out on ebay and hope to find someone who's getting rid of one, and who knows enough about what they're selling to describe it accurately? A gigabit-compatible hub would be ideal -- do those even exist? Wikipedia only talks about 10/100 Mbps hubs.

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IIRC, the gigabit standard requires switching. No CDMA/CD support at those datarates. – Brian Knoblauch Sep 21 '10 at 17:40
+1 @brian - You are correct. – JNK Sep 21 '10 at 17:51
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4 Answers

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Amazon to the rescue.

Unfortunately it's a special product now (people who want them really want them and can't use something else) so the prices may be higher than you expect.

EDIT:

Also you will NOT get a gigabit hub. You won't find PCI-E video cards to use on a 386 motherboard, either...:)

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Heh... so yeah, I guess nobody is making new hubs anymore, and you have to buy old ones. Amazing... even floppy disks are still manufactured somewhere! :) – Josh Sep 21 '10 at 21:16
That's because bootdisks are still useful :) – John T Sep 21 '10 at 22:30
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up vote 5 down vote

If your application for a hub is "inserting a protocol analyzer into a network connection", the modern answer is a switch that supports a monitor mode, in which one switch port is configured to emit all packets to and from another specified port.

The Netgear GS108T (the T is important) is an example of a small switch that does this. Since, as someone else said, there is no such thing as a gigabit hub, this is the only way to get this functionality going forward.

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Yes, but even when I'm using nice managed switches that support monitor mode (i.e. at work) it's not always convenient to use (especially since I'm just learning how to use it); and if I'm working on cheap switches that don't support it, it seems silly to buy an expensive switch that does just for this functionality. Even a 100mbps hub would be handy to have around for quick-and-dirty solutions. – Josh Sep 21 '10 at 21:09
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About 2-3 years ago, we needed these at work, and actually ended up buying some used hubs at the local junk store. These were for 10/100 Mbps. Already, at that time, you couldn't find new hubs anymore. That worked fine, and were convenient. It's good if you don't need anything faster, and you can still find them. – Jamie Cox Sep 22 '10 at 18:31
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up vote 2 down vote

Another answer from Amazon : Dynex DX-EHB4 - Hub - 4 ports - Ethernet - 10Base-T - DC power - external, 1 new from $22.99 and 16 used from $1.84.

Just asking for Ethernet Hub in Electronics will get you 355 products (most of them actually switches).
You may reduce the results further by price etc. to narrow the research.

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+1 - Good find on the cheap one, @harrymc – JNK Sep 21 '10 at 18:30
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up vote 0 down vote

If hubs are hard to come by, another option might be to buy a Wi-Fi router that runs dd-wrt, which it should be possible to configure port mirroring on.

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