[SOLVED] Ethernet cable working on old router but not on new router or PC ethernet port. Why?

Jun 15, 2019
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Hello. So, I have this ethernet cable that I think may be faulty. I use it to connect my router to another modem/router that stays in a house next to mine, the cable is about 30 meters long.
My connection is bad at the moment, I can use the internet but my ping is extremely unstable, which is a pain for me since I play online games. I think this may be due to my router though, cause it's old.
The thing is, I bought a new router but it's not recognizing the ethernet cable, meanwhile the old one does recognize it. The cable is also not recognized if I plug it directly to my computer. What's the problem? Could it be a compatibility thing between the cable and the port? Is that a thing?

Modem/Router: Sagemcom f@st 2704n
My old router: TP-LINK TL-WR740N
My new router: TP-LINK AC750
My motherboard: Gigabyte F2A55M-HD2 Rev 3.0
The cable: The only thing I know is that it's the blue one, I don't know which cat.

By the way, I can't just test another cable cause I don't have it right now and to buy a new one is gonna be expensive in my country. I plan to but first I wanted to make sure what is going on.
 

gggplaya

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Jan 27, 2011
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If the cable isn't outdoor rated, the sheathing of the cable may have become permeable with some holes in it. There may be moisture inside the cable.

The easiest way to test is to just hook up a short spare cable you have laying around between both modem/router and your access point inside the main house, just a few feet apart. If that works, then you know it's the cable.
 

gggplaya

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Is the cable rated for outdoor use??

Based on this statement " I use it to connect my router to another modem/router " it's most likely you have your routers both set to DHCP, perhaps they have the same IP address, or are on different subnets.

If you want both houses to be on the same network, then 1 router must be set as the DHCP and the other router set as just a wifi access point instead, with it's DHCP turned off. Connect the cable from the switch of the main router into the switch of the access point, not the wan port. Give the access point an address that's 1 higher than the main router. If the main router is 192.168.1.1 then make the access point 192.168.1.2. This would probably be the easiest setup. Or instead of buying a router, you can buy just an access point, assuming you can still return the router you just purchased.
 
Last edited:
Jun 15, 2019
15
0
10
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Is the cable rated for outdoor use??

Based on this statement " I use it to connect my router to another modem/router " it's most likely you have your routers both set to DHCP, perhaps they have the same IP address, or are on different subnets.

If you want both houses to be on the same network, then 1 router must be set as the DHCP and the other router set as just a wifi access point instead, with it's DHCP turned off. Connect the cable from the switch of the main router into the switch of the access point, not the wan port. Give the access point an address that's 1 higher than the main router. If the main router is 192.168.1.1 then make the access point 192.168.1.2. This would probably be the easiest setup. Or instead of buying a router, you can buy just an access point, assuming you can still return the router you just purchased.
The DHCP configuration is already like that. That's not the problem. I'm gonna try to provide a better explanation.

Modem/router - - - <long cable> - - - My old router - - - <short cable> - - - My PC = Works but very unstable ping.

Modem/router - - - <long cable>- - - My PC = Does not work. The led light on the pc ethernet port doesn't light up, the computer does not recognize that there is a cable there.

Modem/router - - - <long cable> - - - New router - - - <short cable> - - - My PC = Does not work. The new router does not recognize that there is cable connected in it's port.

About the cable being rated for outdoor use, I don't know. Sorry.
 

gggplaya

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Jan 27, 2011
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If the cable isn't outdoor rated, the sheathing of the cable may have become permeable with some holes in it. There may be moisture inside the cable.

The easiest way to test is to just hook up a short spare cable you have laying around between both modem/router and your access point inside the main house, just a few feet apart. If that works, then you know it's the cable.
 

tgm1024

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Oct 4, 2009
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Thoughts:
  1. Yes, look at the cable (ends, in particular). Do you see the tabs/fingers recessed too far.
  2. Always check the receiving ports. Check to see if the wires that bend down to touch the contact points on the plug aren't themselves depressed too far. If they are, then you might have to go in there and bend them out. Ask someone else here about that, because I've only done that with phone connections.
  3. Check to see if it gets better by pressing the cable in (further than just the "click") and holding it there during the test.
 
Jun 15, 2019
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So, I had a relative who works with phone connections fix the ends for me. He changed the plastic parts for new ones. It fixed my unstable ping but the cable STILL doesnt work when I try to plug it directly to my PC, laptop or WAN port in my new router.
I noticed something though, the cable is not detected when plugged to the WAN port of my new router but it is detected when plugged to the LAN ports. My old router is really old and I want to change it for the new one but I can't if it won't work.
So, the cable is detected by the LAN ports of the routers but isn't detected by the WAN port, my laptop cable port or my PC cable port. Why?
 

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