Not all ethernet ports producing gigabit speeds?

[InternetExplorer]

I got my gigabit sky broadband installed today. I have a rather complex home setup with two ethernet lines going from the router through the house - one directly into a pc and the other into a switch from which it goes to more pcs/waps etc. 

I am using two cat 6 cables

When using port 1 and 3, port 1 gets the full gigabit speed, where as port 3 gets a max speed of 100mbps

When using port 1 and 2, they both only get 100mbps.

Is there something within the configuration that I've missed?

Why are they not both at gigabit speeds???

[mae-3]

@InternetExplorer 

There is no reason all ports shouldn't run at 1Gbps unless the ports, cable or other pieces of equipment aren't set up correctly or are faulty, eg: either all ports on the router running at 100Mbps or 1Gbps and that is the only setting available in the router and you have it set at 1Gbps which is default.

[InternetExplorer]

I've tested both cables and I know they can both run the full gigabit speed, so thus the logical conclusion would be that one of the ports is faulty?

[GD1]

@InternetExplorer  Is it possible that the device you are attaching isn't capable of 1gbps speed?  How are you testing the ports?

[mae-3 · Accepted solution]

@InternetExplorer 

Absolutely agree, it is usually ethernet pin alignment in the ethernet socket that is the issue, eg: a bent pin.

[InternetExplorer]

Connecting Directly to my laptop which is more than capable of gigabit speeds, so I'm assuming its a fault with the router

[InternetExplorer]

The only thing I'm still slightly confused about is why port 1 gets gigabit speed when port 2 is not in use, but only gets 100mbps when port 2 is in use..?

[mae-3]

@InternetExplorer 

A short across pins because it is bent and touching another pin, eg: that causes a pair to not work and knocks the speed down to 100Mbps?