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Turn on PC from network

ray_gillespie

OSNN Veteran Addict
Political User
#3
What's that Wake on Lan option I always see in the BIOS? Is that to wake from sleep mode rather that off? If so, maybe that is of use.
 
#4
PC's do not "turn off" from the front panel button. They go into various levels of low power operation. The power supply is always running.

This allows a lan card that supports wake on lan to activate the power supply to full operation mode. There is usually a physical jumper that needs to be installed if it is a stand alone lan card. Check your MB manual if your LAN is built in.

The bios also needs to be set to allow wake on lan. You can also set wake on keyboard and other options.

A freidn of mine was startled at 3 AM once when his "off" computer suddenly woke up and started transfering files. He pulled the plug on wake on lan after that.
 
#6
Most PCI network cards work for wake on lan also. You need to plug a little jumper cable from the NIC to the MB. The cables are provided with the NIC card.
 

ming

OSNN Advanced
#8
Wake Up on LAN doesn't work very well... ANY signal from a router will switch the PC on. Happened to me before, so I had to disable it.
 
#10
Ming

That's strange. The NIC should only switch the PC on if it receives a message to it's specific IP. Your router or more likely one of the other PCs on the network is probably polling the network to see who is connected.

I beleive that can be disabled but it makes life ugly. Some machines may not see each other on the network when they have been switched off for a while.

OH! Or if there are open ports on the router you may be getting ping attacked by your ISP or hackers. I get a lot of traffic through open ports, a lot of it from my ISP.
 

X-Istence

*
Political User
#12
Ming

That's strange. The NIC should only switch the PC on if it receives a message to it's specific IP. Your router or more likely one of the other PCs on the network is probably polling the network to see who is connected.

I beleive that can be disabled but it makes life ugly. Some machines may not see each other on the network when they have been switched off for a while.

OH! Or if there are open ports on the router you may be getting ping attacked by your ISP or hackers. I get a lot of traffic through open ports, a lot of it from my ISP.
WOL does not work using IP addresses. So it does not matter if a machine on the local network is "polling" the network to see who is connected. Wake on Lan does not need to be enabled and won't make life ugly in any way shape or form. Wake on Lan has nothing to do with connectivity.

Open ports or ping replies even from the outside on open ports that are forwarded to an IP won't have any effect. Since the computer is turned off, the IP is not available in the local network, as no machine is going to be there to reply to an arp request which the router will send before trying to send the packet to the machine, so essentially all that traffic get's dropped on the ground.

There is no reason for your ISP to be checking open ports, unless they are scanning for known vulnerabilities.

Wake on Lan is a special packet that gets sent on port 0/7/9/40000 (40000 is used by newer Intel cards). The packet is UDP and is sent on the IP address 255.255.255.255 (broadcast) which means every machine plugged in will get this packet at it's network interface, as the switch/router will forward it to every port that is currently turned on (Wake on Lan only works if you see blinking lights on the back of your NIC when your computer is in soft-off state).

The packet then contains the information on what Mac Address it wants to wake up, and a possible password.

Code:
ffffffffffff[macaddr x 16]
is what the packet looks like, for a PC with mac address 00:11:22:33:44:55

the packet would look like this:

Code:
ffffffffffff001122334455001122334455001122334455
00112233445500112233445500112233445500112233
44550011223344550011223344550011223344550011
22334455001122334455001122334455001122334455
001122334455001122334455
Now if that machine needed a wake on lan password, you replace the last mac address with the password.

Code:
ffffffffffff001122334455001122334455001122334455
00112233445500112233445500112233445500112233
44550011223344550011223344550011223344550011
22334455001122334455001122334455001122334455
001122334455WAKEUP
Now, I know this is over most people's heads, however I just wanted to point out that any traffic on the local network does not matter, it requires a very specific packet. A router or switch WILL not automatically send these packets.

Before making claims that something is going to be ugly, please read up on how it really works.
 
#13
When you turn a PC off with the front panel power button the network connection lights on my switch stay on indicating the PC's NIC card is active. Hard off is only possible by using the PSU switch or pulling the plug.

So how does a PC go full on if it is not wake on LAN and there is no electrical storm or to trigger a "re-power folowing drop out"? Ming and a coworker have both seen this happen. In the coworkers case disabling WOL stopped the occurences.

And I had reams of zonealarm logs showing constant pings by IP addresses that resolved to SWbell operations before I closed my ports.
 

X-Istence

*
Political User
#14
When you turn a PC off with the front panel power button the network connection lights on my switch stay on indicating the PC's NIC card is active. Hard off is only possible by using the PSU switch or pulling the plug.
Yup, ACPI state S5, or G2. The state the machine has to be in for it to be able to get Wake on Lan packets.

So how does a PC go full on if it is not wake on LAN and there is no electrical storm or to trigger a "re-power folowing drop out"? Ming and a coworker have both seen this happen. In the coworkers case disabling WOL stopped the occurences.
WOL only happens when the magic packet get's sent, so unless some other machine on the network is spamming WOL packets it won't get turned on. During G2/S5 the NIC has no IP address, so it won't respond to ARP packets, and thus the switch has no reason to forward packets to it. Only those on broadcast will get sent to it, but even then only stateless packets, which are sent to broadcast 255.255.255.255.

Is it possible the co-worker also turned on or off another feature? I have one PC I can turn on by kicking a mouse or hitting a button on the keyboard, as well as WOL. I have NEVER seen it turn itself on without getting my input, or a WOL packet. Currently I have 4 machines in my room with WOL capability, not a single one.

And I had reams of zonealarm logs showing constant pings by IP addresses that resolved to SWbell operations before I closed my ports.
Your IP address resolves to SWBell if you are using them, it CAN'T be other machines that are infected with some virus, it must be your ISP? Also ping requests won't traverse your router to your machine. Unless my readings on ICMP and the way ping works are extremely flawed. I would love to see part of these "reams" of zonealarm logs you have, since they apparently contain the magic combination to make ping traverse past it's end point to someone's machine behind NAT.
 

Electronic Punk

willalwaysbewithyou
Staff member
Political User
#15
Interesting thread as its something I may have to look into on an enterprise level at some stage.

Turning off machines at night, waking them up to perform updates, virus scans etc and then turning them off again.

All for the environment etc. something we are being forced into looking at now that we have replaced all our CRT monitors etc.
 

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