Slow (10Mbps) Speedtest on a 100Mbps connection on Gigabit Equipment

[777Bounce]

I have an issue of speed bottlenecks on a small-ish office network that I am looking for troubleshooting advice for.

Here are the known properly functioning links points from the outside inward, all connected with Cat5e cable:

• 
  100/10 service from ISP - I regular hit 100+/10 from other devices.
  Ubiquiti Edgerouter Lite
  Cisco 48 Port Switch
  Asus RT-AC1900 Router

The troublesome segment is as follows:

Asus Router links to:
WAN - Cisco 48 port switch mentioned above - 1 Gbps link
LAN 1 - PC #1 with gigabit controller - 100 Mbps link, speedtest never goes above 10-12 Mbps down, but does get 10 up.
LAN 2 - PC #2 with gigabit controller - 1 Gbps link, speedtest solid 100+
LAN 3 - DVR for security cameras - 100 Mbps (Expected, I think)
LAN 4 - Netgear GS105 Prosafe Gigabit switch - 100Mbps link (Unexpected)

• 
  - Network printer on GS105 port 1
  - PC #3 on GS105 Port 2 Gigabit controller that will blip as high as 25Mbps, but generally sits right at 10Mbps down/10 up.

So, I have two PCs not getting anywhere near their expected download speed.

Today, I swapped cables from the Asus router as follows -
Originally, LAN 1 to PC #1, LAN 2 to PC #2
Swapped, LAN 1 to PC #2, LAN 2 to PC#1.
The Gigabit link followed PC #1, so I am fairly sure PC#2 is the issue, and not the cable or router port, right?

For PC #3, it will be pretty difficult to replace the cable, but that is my suspicion at this point. That said though, if PC #2 has an issue causing slow speeds, PC #3 may have the same issue which may be causing the link to show only 100Mbps... maybe?

So, the big question... what could cause a computer connected to a router with a known good cable in a known good port to get only 10/10 when it should get 100/10 like it's direct neighbor?

All computers are 2 years old or under, and are updated to the latest release of Windows 10 Pro (Spring Update 2018). I have no real history of speeds received, as we just recently bumped from 15/2 with our ISP to 100/10.

Thanks.

 

[Urumiko]

Firstly make sure you are not confusing MBps with Mbps.. i.e Megabytes per second, with megabits per second.

If you are on a 100 megabit connection, 10 megabytes per second throughput is about normal.

Check your ports are auto negotiating to the correct speed and duplex.

Be aware of home routers, I cant comment on your specific router but they often have slow back planes, or have a shared connection to all ethernet lan ports making lan to lan transfers slower.

 

[777Bounce]

Firstly make sure you are not confusing MBps with Mbps.. i.e Megabytes per second, with megabits per second.

If you are on a 100 megabit connection, 10 megabytes per second throughput is about normal.

Check your ports are auto negotiating to the correct speed and duplex.

Be aware of home routers, I cant comment on your specific router but they often have slow back planes, or have a shared connection to all ethernet lan ports making lan to lan transfers slower.

1) I am using Google's speedtest on all machines, which uses Mbps. I'm aware of the difference.

2) The Asus router reports port speed, but I don't see a way to check or force speed or duplex. As I posted, I swapped the cables between PC#1 and PC#2 and the speed stayed with PC#2, so I think PC#2 has an issue.

3) Your point about slow back planes, etc, is over my head and I don't understand how it would apply.

Thank you for your input.

 

[777Bounce]

For anyone who may find this, or care...

I've learned yet another lesson in not making assumptions, especially if you did not install everything yourself!

For PC#3, which is the one going through the Netgear switch that shows a 100Mbps link... I ran a LOOONG known good cable straight from the PC to the Asus Router. BAM! Full expected speeds.

The cable it normally uses makes a terrible path through a drop ceiling and a maze of duct work. Apparently, this was a difficult enough cable to pull/re-run when the cables were upgraded to Cat5e that the installer left a VERY old Dog5e of a cable in place and simply used that. So, I will take on the task to run new cable in it's place.

As for PC#1, Best I can tell, an employee (or someone else with access) at some point swapped the shiny new gigabit ethernet card, with an old clunker 10/100 junker from who knows what machine or where. Easy fix there. It also sheds some possible light on why one of our machines is missing a stick of RAM. I figure someone upgraded their home computer on the sly. Bleh.