Some connections at FastEthernet, some at Gigabit

[siege911]

I just installed a new HP ProCurve 2848 and finally finished all of the wiring for our office (we were almost all on wireless before). All of the computers are configured almost identically. They all have the same onboard Gigabit NIC in each machine, yet some are coming up with 100MB connections and others with Gigabit connections.

All of the cable is the same, the NIC is the same, they are even in the same physical locations, but one PC will be at one speed and another PC at a different speed.

I even had one PC register the connection as a Gigabit connection when it was trying to acquire a network address but when the connection finalized, it showed up as 100MB.

What could possibly be going wrong?

[blackbox_ns]

You may want to try checking the pairing on the cabling as split pairs can cause odd behavior. Here is a good quick reference for pairing:

http://www.duxcw.com/digest/Howto/ne...ble/cable5.htm

Also make sure that all the pairs are wired, 10BaseT and 100BaseT only require 2 pairs to operate (pins 1,2 as a pair / pins 3,6 as a pair), but 1000BaseT requires all 4 pairs to be connected. Another item that you could look at is the Autonegotiation settings for the NICs. In an idea world you would set everything to Autonegotiate, but I have seen where some devices adhere to the standard more so than others. You may want to set a few of the problem PCs to a fixed speed and duplex and see what happens. You may also want to check the settings in the switch aswell, and set it for a fixed speed and duplex.

[johnwill]

I agree, mis-matched pairs can cause all sorts of odd issues. Note that 100mbit only uses four wires, gigabit uses all eight.