Ethernet connections

[HisLordship]

Hi all, I've got 500mb Fibre. 
I was trying to move my router from the hall to the dining room to remove all the wires in the hall. 
If use the white cable supplied then a 15m Ethernet cable from the router to the dining room then through a network hub I get 518mb at the PC. 
If I use the 15m Ethernet cable directly from the ONT to the router in the dining room then use the white cable from the router to the PC I only get 91mb. 
What  am I missing?

[TimmyBGood]

@HisLordship 

91Mbs would suggest that perhaps something is autonegotiating a 100baseT connection rather than 1000baseT over that 15m cable.  Is it definitely 8-core Cat5e (or better)?

[FLC]

Are you maintaining Lan 4/WAN on the router for the ONT connection?

[HisLordship]

If you mean did I use port #4 then yes.

I've tried port #1 & #4 for the ONT connection.

[HisLordship]

Yes, it's better than Cat5e

The cable supplied by sky is only Cat 5e too.

 I'm confused because the 15m cable handles the speed when not directly in the ONT.

[Chrisee]

@HisLordship I would check that the unit you called a "network hub" is in fact a powered gigabit ethernet switch. If it isnt new ones are pretty cheap to buy online depending on how many ports you want but a 5 port Netgear switch costs around £15. 

[HisLordship]

Thanks, I've got a Netgear GS208 8 Port Gigabit switch.

If I go through the switch I get 500mb.

If I don't I get 91mb.

Hence my confusion.