Why do some switches have uplink ports?

Question

So, this appears, on the surface, to be a network admin (serverfault) question, but I'm looking for a lower level answer from a network hacker type.

I was pretty much oblivious to how networks actually work in real life until I started my summer internship. Then, by way of having no other option (internship is at a pretty networking-centric place and I have to put together testbeds for testing [among other things] networks), I became familiar with them. For one thing, the fact that there's no "This goes out to the internet!" port on commercial switches was kind of surprising, until you reasoned about how it works (starts out like a hub til it 'learns' where ips are in terms of the physical port, i guess?).

And after this home-crafted self-discovery (or possibly, error in thinking), I'm back at the extended stay hotel and looking at my cheap little home switch, and it has an uplink port.

Now my question to you, Network hackers (in the good way), is why?

Answer 1

Uplink ports can be thought of special ports for inter-switch connections. Sometimes they may have a higher speed (1G instead of 100M for example). Or they are interchangeable (laid out as modules).

Some have multiple uplink ports (I had one with two), so you may have redundancy or multiple switched connected this way with the same logic (where is the mac address (on wthich other switch)?).

Answer 2

The "uplink" port on your SOHO switch is internally crossed over. It relieves you of having to use a crossover cable to connect two switches. That is the only difference.

BTW: There isn't a "this goes out to the internet" port on SOHO switches either. You're confusing switches and routers/gateways. This confusion may be encouraged by manufacturers putting the two logically separate devices in one piece of hardware, e.g., a router with a 4-port switch. While we're at it, a wireless router w/ 4 port switch is actually logically three separate devices (router, switch, and access point).

BTW #2: A switch (well, except for layer 3 switches, which arguably are only switches to the marketing department) actually learns where MAC addresses are. It neither knows about nor cares about IP.