RBR50 inconsistent WAN port speed

[pzmosquito]

ok, first let me say that I've been searching for similar issue on the forum, but mine is a little different.

I've been running RBK53 for about 2 years with 500/500 Internet speed and everything is good. Now I need to relocate the router so I need a longer ethernet cable to connect to the WAN port. I bought a new cat6 cable and the Internet speed capped at 100Mbps. I thought it must be the cable issue, but then I tried connecting the same cable to the router LAN port to my computer and it runs at 500Mbps full speed. That means the cable is good. I thought it could be the ethernet port negotiation issue. Since the router LAN port is able to run the new cable at full speed, so the router shouldn't be the issue, so I connect the new cable to the router WAN port, using a coupler to connect to the existing cat5e cable that I have been using for 2 years, the speed is still capped at 100Mbps. I tried different coupler, no luck. I then tried connecting the existing cat5e cable directly to the WAN port again, the speed jumps back to full 500/500.

Here's the diagram of my problem!

Can someone help? I'm running out of ideas!

[FURRYe38]

"so I connect the new cable to the router WAN port, using a coupler to connect to the existing cat5e cable that I have been using for 2 years, the speed is still capped at 100Mbps. I tried different coupler, no luck. I then tried connecting the existing cat5e cable directly to the WAN port again, the speed jumps back to full 500/500." 

It's best not to use a LAN cable couplers as this can cause problems. Also don't mix CAT cable versions. Stick with all CAT5e or all CAT6. 

[pzmosquito]

somehow the diagram didn't show in the original post, I'm adding it as attachment here

[FURRYe38]

What happens if you go direct from Modem to back of RBR, not thru in wall wiring or any coupler?

What Firmware version is currently loaded?
What is the Mfr and model# of the Internet Service Providers modem/ONT the NG router is connected too?

[pzmosquito]

Unfortunately I can't, the modelm is outside the house. But it's a good idea to try, I'll take my router outside to give it a try.

Firmware is 2.7.3.22

ISP modem is ARRIS ONT1000GI4-FTR (REV 0A)

[pzmosquito]

UPDATE, I tried connecting from modem to router directly with the new cat6 cable, it's at full 500Mbps speed.

I also tried replacing the coupler with a switch, and it's running at full speed. So it looks like the both in wall wiring ports and the coupler are not able to negotiate 1Gbps with the new cat6 cable. Hmm...

[FURRYe38]

Need to see what kind of cable is in all. Also check termnation jacks as well. 
Glad the switch helped in place of the coupler. 

[pzmosquito]

Yeah, it looks like there's not much I can do except trying different cat6 cables for compatibility reason.

Thanks FURRYe38 for all the suggestions!

[FURRYe38]

Might check into see the cost of in wall caling upgrade. 

Good Luck.