fix-this! Posted August 11, 2009 Share Posted August 11, 2009 i have comcast cable and i noticed that my sufboard cable modem led is always flashing with pc activity, even when my pc is turned off? maybe i never noticed this before but i wonder why it does that, any ideas? i am not behind a router either, i checked under my firewall and the only program active is scvhost atm. Link to comment Share on other sites More sharing options...
soldier1st Posted August 11, 2009 Share Posted August 11, 2009 if it does not affect you then i would not worry about it. mine does it and it does not affect me in any way. Link to comment Share on other sites More sharing options...
qwix Posted August 11, 2009 Share Posted August 11, 2009 its nothing Link to comment Share on other sites More sharing options...
crazzy88ss Posted August 11, 2009 Share Posted August 11, 2009 makes you wonder what the point of the light is if it's flashing when there's no activity... Link to comment Share on other sites More sharing options...
Thunderbuck Posted August 11, 2009 Share Posted August 11, 2009 Do you have a router between the cable modem and your PC? They'll frequently "chat". Another possibility, especially if you have an unsecured wireless access point, is that you have a neighbor stealing bandwidth. Link to comment Share on other sites More sharing options...
fix-this! Posted August 11, 2009 Author Share Posted August 11, 2009 Do you have a router between the cable modem and your PC? They'll frequently "chat".Another possibility, especially if you have an unsecured wireless access point, is that you have a neighbor stealing bandwidth. no router at all. if it does not affect you then i would not worry about it. mine does it and it does not affect me in any way. i want to make sure im not being charged by my cable provider for data that i did not download or use, that's why i asked. i don't remember the led flashing constantly, i did also recently notice my internet / torrent speeds are a ton faster than before too. Link to comment Share on other sites More sharing options...
sc302 Veteran Posted August 11, 2009 Veteran Share Posted August 11, 2009 that modem is constantly flickering. if you put a router between your pc and modem you will see the internet light flicker quite often. I would put a router in if I were you. Link to comment Share on other sites More sharing options...
+BudMan MVC Posted August 11, 2009 MVC Share Posted August 11, 2009 What modem do you have exactly? What is the model number? Is your modem like this? I always have something connected, ie my router -- but not sure if this light actually means traffic is being sent to the device on your lan side.. Or just activity the modem is seeing.. your always going to see traffic on the publc net -- always!! For starters just the arp traffic alone on a comcast network is crazy.. # tcpdump -ni dc0 arp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on dc0, link-type EN10MB (Ethernet), capture size 96 bytes 16:35:34.420586 arp who-has 24.14.199.12 tell 24.14.198.1 16:35:34.446210 arp who-has 24.14.198.40 tell 24.14.198.1 16:35:34.484275 arp who-has 68.60.236.46 tell 68.60.236.1 16:35:34.484734 arp who-has 24.14.66.121 tell 24.14.66.1 16:35:34.525335 arp who-has 71.57.51.62 tell 71.57.50.1 16:35:34.717634 arp who-has 24.13.176.140 tell 24.13.176.1 16:35:34.720594 arp who-has 24.14.66.180 tell 24.14.66.1 16:35:34.896903 arp who-has 71.57.50.112 tell 71.57.50.1 16:35:35.005633 arp who-has 24.13.181.14 tell 24.13.176.1 <SNIPPED> 97 packets captured 417 packets received by filter 0 packets dropped by kernel I counted to 5, so less than 5 seconds and 97 arps seen.. So yeah the lights going to flicker -- most interfaces will still be on even when the computer is off, etc.. Unplug the cable from the modem and see if the PC light stops.. But Im not really sure if its actual PC activity -- or just activity. Does not mean your PC is sending anything back -- can't be since its off ;) But as suggested I would really suggest you put a router between you and the public net. Link to comment Share on other sites More sharing options...
betadan Posted August 14, 2009 Share Posted August 14, 2009 Yes that light is supposed to always flash, even when you aren't doing anything online. I'd be more worried is it wasn't flashing :D Link to comment Share on other sites More sharing options...
Biotoxic_hazard_835 Posted August 14, 2009 Share Posted August 14, 2009 I have both a Surfboard SB5120 and a SBG900 and on both the pc activity light is always flashing even though I'm not doing anything on the computer. Link to comment Share on other sites More sharing options...
Lechio Posted August 14, 2009 Share Posted August 14, 2009 It could also be that someone took control of your modem, injected new firmware into it and is using it as a proxy for something like a botnet. Kinda far fetched, but possible... Try to see if there are any firmware upgrades for that modem, just to be on the safe side. You've also said that you use torrents... That might also be the cause for the activity. Link to comment Share on other sites More sharing options...
Orien Posted August 14, 2009 Share Posted August 14, 2009 You've also said that you use torrents... That might also be the cause for the activity. Not if the computer connected to it is off... Link to comment Share on other sites More sharing options...
Lechio Posted August 14, 2009 Share Posted August 14, 2009 When you use torrents, connections to that IP remain for some time, even after shutting down the PC. Link to comment Share on other sites More sharing options...
betadan Posted August 14, 2009 Share Posted August 14, 2009 To get back to the original question. the PC activity light is just there to indicate that there is in fact a link between the modem and a PC/Router. The reason that even when your PC is turned off the light is lit is that there is still power going to your PC and the NIC is still active, think "wake on LAN". I can almost guarantee you that if you unplugged the power to your PC the light would go off withing 30 seconds. Link to comment Share on other sites More sharing options...
Recommended Posts