Solved Certain ports capped to 100mbps on ASUS Router

[Nathan111]

I'm using ASUS RT-AC87U with the merlin firmware.

LAN 1 and LAN 4 seem to be limited to 100Mbps while other ports (including WAN) run a full 1Gbps.

I'm using some very expensive 10Gbps CAT7 cables here and looks like no matter where I plug the new cables, these 2 specific LAN ports always negotiate a 100Mbps uplink only with whichever device I connect them to. I upgraded the firmware on merlin to the latest one today but it doesn't seem to fix the issue. How to fix this?

 

[OzarkEdge]

I'm using ASUS RT-AC87U with the merlin firmware.

LAN 1 and LAN 4 seem to be limited to 100Mbps while other ports (including WAN) run a full 1Gbps.

I'm using some very expensive 10Gbps CAT7 cables here and looks like no matter where I plug the new cables, these 2 specific LAN ports always negotiate a 100Mbps uplink only with whichever device I connect them to. I upgraded the firmware on merlin to the latest one today but it doesn't seem to fix the issue. How to fix this?

Clean the ports, try cheap cables, reset the router?

OE

 

[Nathan111]

I'm using gold plated really high quality CAT7 cables I get 2-3Gbps from easily.

Just cleaned the ports using pressurized air and now 3 ports are 100Mbps instead of the 2 before.

Should I get rid of merlin and flash the original firmware?

 

[ColinTaylor]

Use whatever firmware you prefer. It won't make any difference to your issue, which is a physical problem with the sockets and/or plugs.

 

[L&LD]

I may be mistaken, but there is no such thing as 'high-quality Cat7' cable. Regardless if you can buy such or not.

Use good quality Cat5e or better quality Cat6 cable to test with.

Another test you can try is to power down the whole network for a few minutes. Making sure to unplug all Ethernet, USB, and AC power connections to all network(ed) devices.

 

[OzarkEdge]

I'm using gold plated really high quality CAT7 cables I get 2-3Gbps from easily.

Just cleaned the ports using pressurized air and now 3 ports are 100Mbps instead of the 2 before.

Should I get rid of merlin and flash the original firmware?

To clean the ports, just inspect them to be sure no debris is in them and that the contacts look ok, clean, and dry. Beware using pressurized air that might damage or deposit gunk on the contacts. If contacts are discolored/corroded, I swab them with some electrical contact cleaner.

Try a cheap cable next.

Does the device at the other end of the cable support Gigabit Ethernet?

OE

 

[Nathan111]

I've already done the usual (clean, reseat, reset router) but the 1st and 4th LAN ports just won't budge and go from 100Mbps to 1Gbps. I used short length cables of different brands, and yes all devices I tested are either 1gbps or 10gbps, but the link only negotiates to 100Mbps Full Duplex.

My question at this point would be if Asus Merlin somehow allows you to set link negotiation on the port level?

 

[ColinTaylor]

My question at this point would be if Asus Merlin somehow allows you to set link negotiation on the port level?

You could try using the robocfg command but I can pretty much guarantee it won't make any difference.

 

[Nathan111]

Some more information about how to use robocfg command, please? I am not a pro user.

 

[Deleted member 51572]

I'm using ASUS RT-AC87U with the merlin firmware.

LAN 1 and LAN 4 seem to be limited to 100Mbps while other ports (including WAN) run a full 1Gbps.

I'm using some very expensive 10Gbps CAT7 cables here and looks like no matter where I plug the new cables, these 2 specific LAN ports always negotiate a 100Mbps uplink only with whichever device I connect them to. I upgraded the firmware on merlin to the latest one today but it doesn't seem to fix the issue. How to fix this?

- do CAT5e cables work correctly (at 1Gbps) with those two LAN ports?
if yes, then stop there, save yourself money & agony, and return the CAT 7 cables.

- how long are the new CAT7 cables and how are they terminated (RJ45 or ARJ45)?

- is the CAT7 shielded (STP); if so, are the connectors on each end properly grounded?
if not grounded, then the shielding may pickup and induce EMI and/or RF into the cable.

- be wary of 'flat' CAT7 cables because most likely, they are not.

if your network gear is not 10Gbps, then CAT7 is way over-spec'd for your purposes

 

[Nathan111]

I just explained above that the same cable gives 1Gbps on another LAN port on the router. Use some common sense, come on.

I concluded the 2 gigabit ports on the router are faulty as they won't go beyond 100Mbps.

 

[Deleted member 51572]

I just explained above that the same cable gives 1Gbps on another LAN port on the router. Use some common sense, come on.

I concluded the 2 gigabit ports on the router are faulty as they won't go beyond 100Mbps.

hmm, assuming no edits were made, i must've misread, i thought you were asking specifically about those "very expensive CAT7 cables" and why their connection rate was limited to 100Mbps. i also thought CAT5e was mentioned somewhere in your query, but don't see that either. oh well, looks like you solved your problem. cheers.

 

[MarkyPancake]

Are you sure the LAN ports' link rate aren't being set by the device connected to these ports?

 

[Nathan111]

replaced the router today, it was a faulty lan port (physical) on the router. all links negotiate at 1gbps now (same end devices, same cables)

 

[SomeWhereOverTheRainBow]

replaced the router today, it was a faulty lan port (physical) on the router. all links negotiate at 1gbps now (same end devices, same cables)

Awesome, I am glad you chose to replace router versus the alternatives. We can't all be the Fonz of fixing equipment when it comes to pluggin' or tappin' equipment.