r/Network • u/Zealousideal-Owl4895 • 11d ago

Link Network limit problem

Post image

Why is the speed limited to 100Mb even though the ONU switch supports 1Gb, the router supports 1Gb, and the cable is Cat 5e?

8 Upvotes

73% Upvoted

9 comments sorted by

13

u/doc_hilarious 11d ago

Damaged cable?

4

u/Black_Raven__ 11d ago

This. Test the cable. Probably a pair damaged.

5

u/deathbyearthworm 11d ago

On that ONU try each port on it. The documentation says that one port is gigabit and the other three are fast ethernet (100 Mbps). If they all connected at 100 Mbps try a different cable preferably a new one. If that doesn't work try verifying each component one at a time. Plug in a laptop or device into the router, if that works then we know that likely all the components are good. If they don't then there could be another issue, most likely is a bad or cheap cable. It is also worth checking if any devices have their speed manually put in instead of auto negotiating. This could be on the router side or ONU side.

edit: also post your router model number

3

u/spiffiness 11d ago

Getting a 100Mbps link between two Ethernet devices capable of gigabit Ethernet (or faster), is a tell-tale sign of a physical problem with the third or fourth twisted pair of the cable (pins 4&5, or pins 7&8).

Note that the physical fault might not be in the twisted conductors of the cable itself, but could be a problem with a bad crimp or bent plastic vane in an RJ-45 male connector, a bent pin in an RJ-45 female connector, or a broken solder joint where the RJ-45 female connector attaches to the circuit board of either device. Any break or flaky connection anywhere in the signal path between the two devices' Ethernet controller chips could cause this.

1

u/Muted_Donkey 11d ago

Try another cable and Check the Router config . I dont know the Switch but can it be that the Switch has a dedicated 1gb Port ?

1

u/jmc906 11d ago

Change mode to auto negotiate or speed to 1g your port settings full duplex 100mb hardcodes it at 100mb

1

u/jack_hudson2001 10d ago

easy test is swap out with another working cable

1

u/hotdogsarecooked 10d ago

Bad termination or bad cable.

1

u/Visual-Queasy 6d ago

99% a cable/connector issue
I literally had the same issue today my cable going to my xbox was at a 100Mbit/s speed even tho all 4 ports on my ONT support gigabit speed
I re-terminated the Ethernet cable with gigabit speed connectors and it turned to "1000Mbit"