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Contributor
deedrew
Posts: 10
Registered: ‎06-24-2012

flashing link light on modem

Why does my modem link light flash consistenly when my comupter is turned on, even when I am not on the internet. I have been getting an "error notice" saying "IP address conflicts with another system on the network." Can someone tell me what all that means? I have notice that I have a difficult time getting onto Comcast site and elsewhere on the internet, it is so frustrating. Is it due to a faulty Comast leased modem(RCA model) or could it be my router?  To me it seems as if my IP address is being shared with someone else. Help if you can. I have already reset the Comcast modem box and even powered it down and still no change.

Silver Problem Solver
reasd
Posts: 6,127
Registered: ‎02-22-2007

Re: flashing link light on modem

[ Edited ]

Hello,

I had this issue awhile ago and here is what I did to fix it but there are no guarantee it will work for you.

Go to each computer and find out the IP address.

Run / Winipcfg
Or
Run / CMD / ipconfig

Depending on your OS.
Your looking for the IP addresses, they should all be different, but you will find that yours and one other have the same.
(Ex 192.168.0.100 or 192.168.1.101, or 192.168.0.XXX, XXX = 2-254)

Enter network properties / TCP/IP and adjust the last octet to any thing different (2-254), but make sure it does not match any other system.

The best bet, is to enable DHCP with in your Cable Router, and then go to each PC, and adjust for DHCP.

This error is stating that your IP is the same as another IP on your little  PC LAN.

 
Connection Expert
EG
Posts: 40,218
Registered: ‎12-24-2003

Re: flashing link light on modem

Also, are you certain that your machine is clean and free of any possible viruses and / or malware ?

Contributor
deedrew
Posts: 10
Registered: ‎06-24-2012

Re: flashing link light on modem

If there were any viruses would not Norton security stop them or notify me of such?

Connection Expert
EG
Posts: 40,218
Registered: ‎12-24-2003

Re: flashing link light on modem

Not necessarily. A/V apps are by no means flawless.

Contributor
deedrew
Posts: 10
Registered: ‎06-24-2012

Re: flashing link light on modem

The bling link light occurs even when my computer is shut off. Only the Comast modem and my router are on and the LINK light contiues to flash as thou the two are communicating.The other computer is off line and unplugged, so I know its not being used.

Contributor
deedrew
Posts: 10
Registered: ‎06-24-2012

Re: flashing link light on modem

The bling link light occurs even when my computer is shut off. Only the Comast modem and my router are on and the LINK light contiues to flash as thou the two are communicating.The other computer is off line and unplugged, so I know its not being used. I have yet to look at the IP numbers as you have suggested, but I.m thinking that if both computers are powered off and the LINK light on the modem and the router are flashing that tells me that somewhere outside this house possibly someone else is on my IP address. Does that make any sense to you? Is it possible that Comcast could have connected someone else to my IP address?

Connection Expert
EG
Posts: 40,218
Registered: ‎12-24-2003

Re: flashing link light on modem

The router and modem are indeed talking to each other even if nothing else is on. The router is seeing normal background traffic on the cable segment that you share with your neighbors. It's nothing to be concerned about.

Contributor
deedrew
Posts: 10
Registered: ‎06-24-2012

Re: flashing link light on modem

Thankyou for your reply, I understand that the 2 components are talking but I forgot to mention that this only started in March of this year, prior to that this talking between components has never taking place unless I was actually online.

New Visitor
rcalvil
Posts: 1
Registered: ‎07-07-2012

Re: flashing link light on modem

Then someone else might be using your internet connection. Try putting a password on your router or changing it if you already have one.

Contributor
deedrew
Posts: 10
Registered: ‎06-24-2012

Re: flashing link light on modem

How do I put a password on my router? Thanks, if you can help.

Regular Problem Solver
Posts: 787
Registered: ‎03-14-2005

Re: flashing link light on modem

While it is certainly possible that someone is taking advantage of your unsecured wireless router, the usual cause of the constantly flashing LINK light is the routine broadcast packets that are a necessary part of IP networking on a shared medium. Whether the modem flashes its LINK light for these packets is a function of the modem firmware. Some firmware loads do, and some do not, so the change in behavior could also be due to your modem receiving a firmware update.

 

Note: While that flashing light makes it look like a lot of traffic, those broadcast packets actually use only a small fraction of 1% of the link bandwidth.

Contributor
deedrew
Posts: 10
Registered: ‎06-24-2012

Re: flashing link light on modem

Melvin, this sounds logical about the firmware but I see one question pop into my head. Why does this firmware run all day and night with only my modem and my router powered up and the computer powered down? Where is all this firmware info going if there is no computer to sent it to? Thanks for any thoughts.

Connection Expert
EG
Posts: 40,218
Registered: ‎12-24-2003

Re: flashing link light on modem

[ Edited ]

As I stated earlier in this thread, the modem and the router are always talking to each other no matter if anything on the LAN is turned on. This traffic is what is triggering the light. FWIW, the "firmware" is not going anywhere, it is always present / loaded in both the modem and the router. The instructions (code) within the router's firmware is what tells that indicator light to behave a certain way.

Contributor
deedrew
Posts: 10
Registered: ‎06-24-2012

Re: flashing link light on modem

Thankyou for your information, I understand much better now what is going on. My only concern was that this communicating never was as pronunced as it is now. Your answer has helped ease my worries. Have a blessed day and week to come,thankyou.

Connection Expert
EG
Posts: 40,218
Registered: ‎12-24-2003

Re: flashing link light on modem

[ Edited ]

No worries as long as your WiFi is now locked down ?

Contributor
deedrew
Posts: 10
Registered: ‎06-24-2012

Re: flashing link light on modem

I do not understand what you mean by:as long as your WiFi is now locked down?

New Visitor
Stav
Posts: 4
Registered: ‎07-17-2012

Re: flashing link light on modem

To see what's going on you can install Wireshark on your PC and connect your PC straight to the modem.

 

I am having the same problem and the root cause is a contant flood of incoming broadcast ARP requests.

Connection Expert
EG
Posts: 40,218
Registered: ‎12-24-2003

Re: flashing link light on modem

[ Edited ]

Stav wrote:

 

I am having the same problem and the root cause is a contant flood of incoming broadcast ARP requests.



It's not a problem nor is it "flooding". See the response in your thread.

 

This ARP and DHCP traffic actually consumes very little bandwidth.

Connection Expert
EG
Posts: 40,218
Registered: ‎12-24-2003

Re: flashing link light on modem


deedrew wrote:

I do not understand what you mean by:as long as your WiFi is now locked down?


Do you have the wireless security encryption feature/s of the router enabled ? WPA2 with AES specifically ?

Contributor
deedrew
Posts: 10
Registered: ‎06-24-2012

Re: flashing link light on modem

Yes, I have the WPA2 enabled.

Connection Expert
EG
Posts: 40,218
Registered: ‎12-24-2003

Re: flashing link light on modem

[ Edited ]

O/k so then some neighbor leeching your connection is not the cause..