Problems with wired connections // Wireless connections are fine

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mpf04

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Nov 24, 2013
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We have recently upgraded our router to a Belkin 1750AC DB. Setting everything up went great, for both our three computers connected and our various cell phones/tablets wirelessly. About a day or so after the installation we began to have issues with two of our computers connected through the router with ethernet cables dropping internet connection while the third will stay connected without issues. It has started to happen quite frequently(three-four times daily) now. After doing a hard reset on the router the connections will work again, though for how long is a mystery. We have tried setting the two computers up with a static IP to no avail. The strange thing is that when they lose connectivity, the wireless connections still work along with the other computer.

We believed the issue to be in the modem so we called our ISP, they came out, swapped it out and still did not fix the issue. Switched ethernet cables and did not help either.

Any suggestions would be greatly appreciated!
 
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I am going to assume that you still have lights on the router/pc for the Ethernet cables and your machines are not giving you the "ethernet cable disconnected" message.

The difference between the wireless and the wired in many routers is they have a different mac address. I am going to suspect you have a ARP issue. First to do is issue ARP -a and see what you have. You should see the gateway IP mapped to the mac address of the router. If you would delete this if it reappears then you machine can talk to the router at a very basic level. You can ping the router gateway address to force it to make this appear. Even if the ping fails the ARP may still resolve. You can statically set the ARP entries but I would avoid doing that...
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bill001g

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Aug 9, 2012
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I am going to assume that you still have lights on the router/pc for the Ethernet cables and your machines are not giving you the "ethernet cable disconnected" message.

The difference between the wireless and the wired in many routers is they have a different mac address. I am going to suspect you have a ARP issue. First to do is issue ARP -a and see what you have. You should see the gateway IP mapped to the mac address of the router. If you would delete this if it reappears then you machine can talk to the router at a very basic level. You can ping the router gateway address to force it to make this appear. Even if the ping fails the ARP may still resolve. You can statically set the ARP entries but I would avoid doing that except for testing.

Now it may look fine on the PC side but you can have the same issue on the router. Some routers are easier than others to find and mess with the ARP tables.

I am going to bet your PC that is working is somehow disrupting the other 2.
 
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mpf04

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Nov 24, 2013
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You are correct that the lights on the modem and the router both are still working like normal. Just the two computers randomly losing connectivity.

When running an arp -a on one of the computers that loses connectivity I do see the IP mapped to the router and it is set to dynamic. Then after that I see 5 entries that are listed as dynamic. I'm not quite sure on how to delete the entry for the router IP. I'm assuming arp -d and then the IP? Have tried doing that and nothing seems to happen. A ping to the IP runs through fine.

Can post the results of the arp -a if needed, just wasn't sure what all was needed.
 
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bill001g

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Aug 9, 2012
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Make sure the mac address that is mapped to what you think is the router IP is really the router. Although rare a poisoned ARP entry will contain the wrong ip-mac mapping.

If you can ping the router you have a good connection and all the IP and such are good. I guess you could try to ping something like 8.8.8.8 or 4.2.2.2 to see if traffic will pass the router at all. These are open DNS servers. If ping works and other stuff does not i would be suspect of some form of firewall filter on something. You could also try to set one of these 2 addresses as your DNS server in your PC and see if it makes any difference.
 
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mpf04

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Nov 24, 2013
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Well the two computers lost connectivity again and so I decided to do an arp -a and a ping to both the router and to the 8.8.8.8 address you gave me. The arp - a would sometimes show the router IP address and other times it wouldn't. A couple of pings while it was acting up:

Pinging 192.168.2.1 with 32 bytes of data:
Reply from 192.168.2.1: bytes=32 time=1185ms TTL=64
Request timed out.
General failure.
Request timed out.

Ping statistics for 192.168.2.1:
Packets: Sent = 4, Received = 1, Lost = 3 (75% loss),
Approximate round trip times in milli-seconds:
Minimum = 1185ms, Maximum = 1185ms, Average = 1185ms

And then one to the 8.8.8.8 address you listed.

Pinging 8.8.8.8 with 32 bytes of data:
General failure.
General failure.
General failure.
Reply from 192.168.2.165: Destination host unreachable.

Ping statistics for 8.8.8.8:
Packets: Sent = 4, Received = 1, Lost = 3 (75% loss),

And of course, a hard reset of the router solved the connectivity issues.
 
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