Wake-On-LAN

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MurrayM

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Topic # 152188 18-Sep-2014 17:51

After finally getting my router (Vodafone Echolife HG556a) to update dyndns.com with it's IP address, I'm now trying to set things up so I can send a Wake-On-LAN message to my computer (actually a Wake-On-WAN because I want to do it remotely).

On my router I've set up a static IP and assigned it to my computer's MAC address and tested that it is indeed being assigned the address I set up (192.168.1.99). I've set up my router's NAT to forward port 9 to 192.168.1.99.

The IP address showed up in the router's ARP table. I then powered the computer off and sent a magic packet to wake it up but nothing happened. I checked the ARP table and the IP address was gone.

I then figured out that the static IP address that I had reserved wasn't being kept in the router's ARP table, it would vanish when the computer was turned off, so I used telnet and logged into the router and issued an arp add 192.168.1.99 mac-address command and then confirmed that it had been set up as a permanent address. When viewing the ARP table via the router's web interface it shows as "Permanent".

I then turn the computer off and tried sending a magic packet to it and it worked! The computer started up fine.

But if the router turns off then it forgets the IP address that I'd added to the ARP table. It seems that permanent isn't really permanent. I tried adding it back in and then issuing a save command to save the router's setting to flash memory and then rebooting, but it still forgets the IP address.

Can anyone suggest anything that will get the router to remember the IP address permanently?

nedkelly

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Reply # 1131664 18-Sep-2014 18:19

I thought wake on lan was 0 or 1 not 9.

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MurrayM

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Reply # 1131792 18-Sep-2014 20:44

nedkelly: I thought wake on lan was 0 or 1 not 9.

My understanding is that it can be any port you want as it's only used so that the router can direct the magic packet to the correct machine (i.e. set up a firewall rule to direct anything coming in on port xx to machine yy).

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richms

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Reply # 1131796 18-Sep-2014 20:50

You have only set a static reservation in the DHCP server, not a static ARP assignment, so the router has no idea what mac address to send the magic packet to.

Last I played with WOL from outside, it was done by fowarding a UDP port to the broadcast address of the lan, and then send the magic packet to that port and it would be broadcast and would work sometimes but not always.

Richard rich.ms

MurrayM

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Reply # 1131816 18-Sep-2014 21:10

richms: You have only set a static reservation in the DHCP server, not a static ARP assignment, so the router has no idea what mac address to send the magic packet to.

Last I played with WOL from outside, it was done by fowarding a UDP port to the broadcast address of the lan, and then send the magic packet to that port and it would be broadcast and would work sometimes but not always.

Hmm. I set up a rule in the router to forward everything sent to UDP port 9 on to the computer's IP address. The wake-on-lan does actually work, the computer wakes up ok. The problem is that if the router reboots then the ARP table is cleared and the router forgets that IP 192.168.1.99 is set up for the computer. If I turn the computer on then the router recognises it and assigns it 192.168.1.99

I did try sending to the broadcast address, but the router won't allow me to forward packets to 192.168.1.255, it just said it was an invalid address. I read somewhere that many routers block this.

So if an arp add command doesn't add a static ARP assignment, what does?

richms

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Reply # 1131818 18-Sep-2014 21:16

That adds it for the current session in memory without any aging so it will not expire like the dynamic arps do.

Most routers dont have any way of making it a permanent addition that will persist across restarts, as the config is stored in nvram which needs the scripts to support the values and actually issue the commands on bootup

Is it something you can add openwrt/similar to and get a proper file system that persists across restarts that you can add your own scripts to?

Richard rich.ms

ubergeeknz

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Reply # 1131819 18-Sep-2014 21:17

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Why power off the router? They are designed to be left on, and shouldn't be using bugger all power when idle.

richms

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Reply # 1131824 18-Sep-2014 21:20

One person supports this post

Because they crash and need restarting sometimes, so a plug in timer on an adsl router to reset it in the morning means your remote place is offline for a max of a day when it does crash?

Richard rich.ms

MurrayM

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Reply # 1131829 18-Sep-2014 21:30

ubergeeknz: Why power off the router? They are designed to be left on, and shouldn't be using bugger all power when idle.

I don't power off the router, it only loses power if there's a power cut or I need to move the router or make a change to the router's settings and it wants to reboot, otherwise it's on all the time. I was just trying to make it permanent because the whole idea of the exercise is for remote access when there's no one home to turn the computers on. If I've gone away for a couple of weeks and there's been a power cut while I'm away then the router will forget what I've got set up and I won't be able to get in.

MurrayM

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Reply # 1131831 18-Sep-2014 21:35

richms: That adds it for the current session in memory without any aging so it will not expire like the dynamic arps do.

Most routers dont have any way of making it a permanent addition that will persist across restarts, as the config is stored in nvram which needs the scripts to support the values and actually issue the commands on bootup

Is it something you can add openwrt/similar to and get a proper file system that persists across restarts that you can add your own scripts to?

Ah, thanks for explaining that, makes sense now.

I believe that openwrt is available for this router, but I was hoping not to muck around too much with it.

I wonder if I can telnet into the router externally and set it up if I need to? I've got the dynamic DNS set up so the router updates a hostname with it's IP, so that part is done. Anything else I need to do?

richms

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Reply # 1131836 18-Sep-2014 21:46

Well you dont want to be telnetting in directly. If it supports VPN then you could get in over that, but in that case you could possibly send the WOL directly without relying on the router.

Richard rich.ms

MurrayM

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Reply # 1131923 19-Sep-2014 07:28

richms: Well you dont want to be telnetting in directly. If it supports VPN then you could get in over that, but in that case you could possibly send the WOL directly without relying on the router.

Why don't I want to telnet directly in? I realise that opening external access is a bit of a security risk, but I'd set up a strong password to counter the risk.

I don't think VPN is an option.