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Embarrassing stupid question regarding 10/100 MBit hubs/switches...

E

Elledan

Banned
If you've got a 10/100 MBit hub/switch and connect a couple of 10 Mbit and 100 Mbit NIC's to it, what is the speed of the network? Is it as 'fast' as the slowest NIC (10 Mbit), or what?

Thanks 🙂
 
There are autosensing 10/100 hubs meaning you can run both speeds on your network. The speed would be determined by the slowest common denominator on one side of the file transfer. In other words, if two PC's are transferring data with 100 meg cards then they would be 100 meg but if one is 10 meg they would only be transferring as fast as that one could send or recieve. Thats assuming no on else is transferring data because a hub shares the bandwidth vs a switch which is dedicated at each port. Also, these network BBS's are littered with troublecalls about problems that are caused by these autosensing hubs not doing what they advertise doing. Invariably forcing 10 meg on the 10/100 NIC's will solve the ills so its not perfect by any means, especially with cheap 10/100 hubs, but its possible to have a mixed network and get the full pull from a 100mb card on a network with some 10mb NIC's.
 
A 10/100 hub will set all ports to the speed of the slowest device. A 10/100 switching hub will allow each port to autosense independently (while still broadcasting traffic to all ports). A 10/100 switch will allow each port to autosense independently, but traffic will only be sent to the port for which it is intended, creating separate collision domains.

The speed that a given device will be able to communicate with another is as slow as the slowest link along the way. It would work like this:

Let's say we've got 3 PCs, PC A is 10Mb, PCs B and C are both 100Mb. The speeds for communication using the various devices would be like this:

10/100 Hub:
A to B - 10
A to C - 10
B to C - 10

10/100 Switching Hub:
A to B - 10
A to C - 10
B to C - 100

10/100 Switch:
A to B - 10
A to C - 10
B to C - 100

You can see that on the hub, PC A knocks everyone down to 10 Mb, whereas on the switching devices, only communication with PC is limited to 10. On the switching hub, PC A can see the communication between B and C but ignores it, on the switch, it can't even see it.
 
Thank you for your explanation, nettech98! I smell FAQ material 🙂

I'm left with one question, however: I've actually never seen a switching hub, just hubs and switches, are switching hubs just rare?
 
Interesting. I obviously thought otherwise but I never really did any research on it or benched it. I'll check out the speeds of our mixed network at the office.

Yeah, looked around. Nothing that actually said that this was the case but in a "not so many words" deal. Still would like to read it in print specifically but does look like all ports must be running at 100 Mb for any to work at 100Mb. Bummer huh?
 
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