Netgear R7800 install firmware and Static ARP entry

Hi all :),

I am new here and was wondering if somebody can give me some advise.

I am having some troubles with my router a Netgear R7800 that still has the original firmware. Untill not so long a go I had the option to awake my desktop from distance by sending a magic packet trough the WAN. However for some reason once the desktop will go to sleep I won't be able anymore to awake it by WAN but only trough lan. After a lot of searching and asking on forums it seems that I need to enter a static ARP in the router.

Unfortunately Netgear doesn't make it really easy for me as till today it wasn't very successful to do this. As the garantee already passed Netgear won't provide any help without paying for that so as alternative I looked up a solution. So here I am informing and checking what I can do best and in this particular case a lot of people are convincing me to install a custom firmware.

However before I do nothing I do have some questions and hope someone is so kind enough to help/advise me as I am not that experienced with routers and this will be my first install.

So I would like to know if:

  • once I install the custom firmware will the ARP table be reset/deleted or even replaced ?

  • can I enter a static ARP using this firmware ?

  • and suppose for what reason can i downgrade it from the custom firmware to its original firmware ?

I hope you can help me with this challenge

Thanks in advanced :smiley:

I can tell you for sure that WoL does not require any static entry in the arp table.

The magic packet is a broadcast frame containing anywhere within its payload 6 bytes of all 255 (FF FF FF FF FF FF in hexadecimal), followed by sixteen repetitions of the target computer's 48-bit MAC address, for a total of 102 bytes.

More to read:

Maybe it is a problem of your forwarding and not the static arp thing.

The OP is likely referring to the “hack” where a packet is sent to one interface and the ARP table and NAT are used to send it out on a different subnet.

Use of SSH and a WOL package or code is much more robust and secure.

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@trendy I understand you maybe say this however i am informing also on 4 other forums and am getting everywhere the same response. Its even more that i tried everything at home to get this working again as this already worked before.

I even found a youtube video explaining exact the same problem that i have and even a solution, however i can't apply that solution to my router.

@jeff can you maybe explain a little bit as i am not that experienced with routers ..... sorry :s

You can SSH into your router. Then install the etherwake package and send the magic packet to the host you want.
etherwake -i ethX.Y 00:0f:3d:ce:ef:ee
Where ethX.Y is the router interface facing the host.

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#!/bin/sh

wakeip="10.77.77.77"
wakemac="00:11:22:33:44:55"


if (! opkg list-installed | cut -d' ' -f1 | grep -q ip-full); then
	opkg update; if [ $? -ne 0 ]; then echo "opkg update failed" && exit 1; fi
	opkg install ip-full; if [ $? -ne 0 ]; then echo "opkg install ip-full failed" && exit 1; fi
fi

if (ip neigh | grep 'PERMANENT' | grep -wq "$wakeip"); then
	echo "Static arp entry exists"
else
	if (ip neigh | grep -wq "$wakeip"); then
		ip neighbor replace $wakeip lladdr $wakemac nud permanent dev br-lan
	else
		ip neighbor add $wakeip lladdr $wakemac nud permanent dev br-lan
	fi
fi

ip neigh | grep -w "$wakeip"

exit 0
1 Like

Ok i see i need to look some things up on google as my experience wich such terms are minimum, anyway thanks for some new leads will check them out to see if i understand them

Basically, what is happing is this.

Your devices' MAC address is added to a MAC address table; So say your computer is plugged into ethernet 2 on the router, it would be a bit like this in the simplified logic.

xE - xx - xx - xx - xx - xx via Ethernet 2

After the default timer(Cisco switches) of 300s, that Mac address will no longer be in that table, and thus the device will not know where to send the received packets that are addressed to that MAC, so when this happens, the device would need to perform what is known as FLOODing in-which this is where the device will send the Packet out all interfaces except the one it came in on, but in this case, your device will be sleep mode with WOL(Wake On Lan) configured, and your device will ignore the Packet as its looking for a magic packet.

So, in this case, the WOL will never work because when you send a WOL packet, the router/modem handles this a bit differently than a normal packet, because you're now working with a Layer 3 information as your transport. So now your need a IP address to route the WOL packet to your device, but if your device is in sleep mode, it's not actively sending traffic on the network, so the MAC address table will remove the entry, and the ARP(Address Resolution Protocol) will be removed as well after the ~15 minutes. What ends up happening is that:

1- your devices is sleeping, ignoring all traffic except the WOL packet
2- the router/modem now after x time has no idea your device exists. AKA It no longer cares.
3- Now your left with no ip entry's, nor any Mac address to your device.
4- you're trying to send a WOL packet witch uses IP addressee and Mac address's
What this sums up to is that you're basically writing a letter with a destination to some address, in some place, somewhere along the milky way, and expecting USPS to know where you intend to send it.

So to solve this you need to use was called a static ARP entry, which will map the MAC to the IP indefinitely, or until the command is removed. This way, there will always be an address to send all traffic to your device Layer 2(MAC addresses only) and Layer 3(IP addresses only)(I simplified this for home routers)

When configuring WOL the Packet needs to follow some logic. IP address(where am I going), MAC address(who am I talking to), payload(I am waking you up).

If you're trying to WOL a device from outside your network, you will need the public IP address and MAC address of the device you're trying to wake.

Example public ip 172.21.200.200, xE - xx - xx - xx - xx - xx

If you're trying to wake up a device from inside the same network, you will need the private IP address,, and MAC address of the device you're trying to wake.

Example private ip 192.168.1.1 , xE - xx - xx - xx - xx - xx

note: if you have a multi-layer private network using, let's say a 10.0.0.0 network connected to a 192.168.0.0 network and then to your ISP, you most likely will not need to be reading this, but just in case to solve your WOL issue, you will need to set up port forwarding to create the path for the WOL packet normally ports 7 or 9

I hope someone finds this useful.