RESOLVED (Smoked 1gb WAN port) I'm stumped--slow Modem to Router speeds RT-AX86U

Grievous Angel

Regular Contributor
Ok I have an issue that's got me at the end of my rope. My only other option as I see it is replacing the router, but I thought I'd ask here first as I have an RT-AX86U that isn't very old.

Here's the scenario:
1) I had a lightning strike that blew out the Spectrum modem. No power light. Swapped the modem, had it re-provisioned (supposed to be 300mbps). I did a speed test (asus interface, router to modem) and it consistently said around 90mbps. Charter scheduled a rep.
2) the rep checked the signals, said they were fine. COAX was around 960mbps. However, wired out of the modem to his hand held tester was the same 90mbps I was seeing. Ok, I got unlucky with a bad router again right? Wrong. Replaced the router again, re-provisioned. This time, it did say 300mbps per his testing. I thought we were in business. As soon as I fired up my router however, I was back down to 90mbps.
3) We had them refresh the modem again....but the bottom line is, it would send 300mbps worth of data to his tester RIGHT AFTER THE MODEM REBOOTED. It wasn't until I connected my router that it would drop back down to 90mbps or so. (we could disconnect my router, plug his tester back in, and sure enough, it would be sending 90mbps again). We tried this test a couple of times (reset modem, direct connect his tester at 300mbps, then connect my AX86U and it would test 90mbps, then reconnect his direct hand held tester and would then see 90mbps, until he reset the modem again).
4) Couldn't be my router CAUSING the modem to send less data right? Well he got a Spectrum router off the truck, and sure enough I could get 300mbps through it.
5) At that point I knew it had to be something with my router. For giggles I did a complete factory reset with the latest ASUS firmware. I still have the same issue. For giggles I swapped out the ethernet cable and it made no difference.

Is my router fried? Does it make sense that something my router is doing could signal the modem to slow down to 90mbps (until it's rebooted?).

Trying to avoid an expensive router replacement (it's still 250) when for all I know it will do the same thing.

Any thoughts?
 
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Tech9

Part of the Furniture
What's you WAN port connection speed?

1658615946740.png


Sound like it's dropping to Fast Ethernet 100Mbps at some point. Did you try with a different cable? Both 2.5GbE and Gigabit WAN ports?
 

Grievous Angel

Regular Contributor
What's you WAN port connection speed?

View attachment 43008

Sound like it's dropping to Fast Ethernet 100Mbps at some point. Did you try with a different cable? Both 2.5GbE and Gigabit WAN ports?

I can try the 2.5 (do I have to change a setting for that or just swap the cable?). I did try a different cable.

Edit: It does say 100mbps for my WAN port. Why would it be doing that?
 

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Tech9

Part of the Furniture
Bad cable most likely, but it can be damaged WAN port as well. Try 2.5GbE WAN port first and if you see 100Mbps again - replace the cable.

1658617306415.png


What about your other 100Mbps connections? Are the devices connected Fast Ethernet or Gigabit capable? Are your LAN ports clean of dust?
 

Tech9

Part of the Furniture
Sounds like a port/cable issue to me. Dirty ports perhaps, no good connection to all pins.
 

Grievous Angel

Regular Contributor
Bad cable most likely, but it can be damaged WAN port as well. Try 2.5GbE WAN port first and if you see 100Mbps again - replace the cable.
Nailed it. I did swap out cables (three different ones on the 1gb wan port, which upon inspection is clean and dust free) but it turns out it works fine on the 2.5 port. Any downside to using this port?

On Thursday night, lightning struck, pretty close to my house. Immediately lost wifi. Modem power light would not come on.

I guess it's reasonable that my 1gb WAN port got smoked in the process? Odd that it would still work "fast ethernet.

Also, the reason the modem was "sticky" to less than 100mbps is I bet it adjust its connection speed down to 100mpbs if it sees fast internet, and restores it on a reboot. I did have to reboot the modem again even after I saw 2.5 on the asus console.

Thank you guys so much!
 
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Tech9

Part of the Furniture
You can use the 2.5GbE port for WAN, it is a second WAN port anyway. I'm not very convinced the port is damaged, but it's possible. I would clean the router and test again with a good cable. If all I can get is 100Mbps - probably port damage. If it's intermittent 1000/100Mbps - probably dirty port. What you see around 90Mbps is typical Fast Ethernet connection speed. The maximum speed is 94Mbps. The maximum speed for Gigabit is 940Mbps.
 

Grievous Angel

Regular Contributor
You can use the 2.5GbE port for WAN, it is a second WAN port anyway. I'm not very convinced the port is damaged, but it's possible. I would clean the router and test again with a good cable. If all I can get is 100Mbps - probably port damage. If it's intermittent 1000/100Mbps - probably dirty port. What you see around 90Mbps is typical Fast Ethernet connection speed. The maximum speed is 94Mbps. The maximum speed for Gigabit is 940Mbps.

It wasn't intermittent at all. It was consistently maxing out in the 90-94bps range. I'm thinking it got smoked when the modem attached to it got smoked (by lightning). I guess I'm thankful I have a "spare" wan port on this thing. The added expense paid off!

Thank you kindly for the help. I don't need to run a true dual WAN so I should be fine just using the 2nd (2.5) wan port.
 

Tech9

Part of the Furniture
I'm thinking it got smoked when the modem attached to it got smoked

Possibly. Check your other ports with 100Mbps connections though. I don't know what devices you have connected there.
 

Grievous Angel

Regular Contributor
Possibly. Check your other ports with 100Mbps connections though. I don't know what devices you have connected there.

Good tip. I think they're as expected. I turned everything on--Xbox Series X (Gb), Shield TV (Gb), Hue Sync bridge (fast ethernet...never thought about it but I bet that's right), and the last one is an LG TV that I had wired...I just unwired it as I don't use any of its smart features anyway. I can imagine them using fast ethernet in a mid level TV anyway.

Edit: what the heck is port 5? There's only 4 ports on the switch.
 

Tech9

Part of the Furniture
IoT and TV are Fast Ethernet for sure.

LAN 5 is your Gigabit WAN port. When not used as WAN, it turns into a regular LAN port.
 

Grievous Angel

Regular Contributor
LAN 5 is your Gigabit WAN port. When not used as WAN, it turns into a regular LAN port.

Well then. I may wire one of my gig devices to it and see if they get limited to fast ethernet. That would further confirm if the port is smoked. Right?
 

bbunge

Part of the Furniture
IoT and TV are Fast Ethernet for sure.

LAN 5 is your Gigabit WAN port. When not used as WAN, it turns into a regular LAN port.
No, LAN5 is the 2.5 GB port that can be used as a WAN port
 

Tech9

Part of the Furniture
No, LAN5 is the 2.5 GB port that can be used as a WAN port

And when your 2.5GbE port is used for WAN port, what is LAN 5?

1658621677156.png
 

bbunge

Part of the Furniture
Well then. I may wire one of my gig devices to it and see if they get limited to fast ethernet. That would further confirm if the port is smoked. Right?
Looks like your WAN port is fried. One recommendation is to factory reset the router and set it up again to see if you can get the 1 GB bandwidth back to the WAN port.
If not you can continue to use the 2.5 GIG port as a WAN port. If it works you haven't lost anything. However, once fried will the damage progress to other parts of the board? Asus may give you a warranty replacement...
 

hyelton

Senior Member
Ouch yeah WAN port done for. Had this happen on my rackmount netgear nas last month. Which I kept at my parents house, Lighting hit an outside camera killed the PoE injector, 8 port switch, and crippled one of the ethernet ports on my nas. The camera was still fine! and no other device on that switch was affected oddly. A few days later another storm came through crippled the 2nd ethernet port on the nas so now both where stuck at 10/100 so had to replace it.
 

Tech9

Part of the Furniture

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