Iptables – How to forward UDP Wake-on-Lan port to broadcast IP with IPTABLES

iptablesport-forwardingroutertelnetwake-on-lan

I'm trying to setup Wake-on-Lan for some of the LAN computers at home and it seems that I need to open a UDP port (7 or 9 being the most common) and forward all requests to the broadcast IP, which in my case is 192.168.1.255.

The problem is that my router does not allow me to forward anything to the broadcast IP.

I can connect to my router through telnet and it seems this router uses IPTABLES, but I don't know much about it or how to is.

Can someone help me out with the proper iptables commands to do what I want? Also, in case it doesn't work, the commands to put everything back would be nice too.

One last thing, rebooting the router will keep those manually added iptables entries or I would need to run them every time?

Best Answer

# iptables -A PREROUTING -t nat -p udp --dport 6  -d <original destination> -j DNAT --to-destination 192.168.1.255

That will take a WOL packet destined for and reroute it to the broadcast of your network.

Also if you are using a Red Hat derived system you will need to save the iptables entry using

# service iptables save

Related Solutions

Iptables – Broadcast UDP over VPN

As @James say, you will probably want to investigate using multicast. A normal IP broadcast does not cross a router and a VPN termination point is (usually) routed rather than bridged, for network efficiency reasons.

Linux – How to Port Forward with Iptables

First of all - you should check if forwarding is allowed at all:

cat /proc/sys/net/ipv4/conf/ppp0/forwarding 
cat /proc/sys/net/ipv4/conf/eth0/forwarding

If both returns 1 it's ok. If not do the following:

echo '1' | sudo tee /proc/sys/net/ipv4/conf/ppp0/forwarding
echo '1' | sudo tee /proc/sys/net/ipv4/conf/eth0/forwarding

Second thing - DNAT could be applied on nat table only. So, your rule should be extended by adding table specification as well (-t nat):

iptables -t nat -A PREROUTING -p tcp -i ppp0 --dport 8001 -j DNAT --to-destination 192.168.1.200:8080
iptables -A FORWARD -p tcp -d 192.168.1.200 --dport 8080 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

Both rules are applied only to TCP traffic (if you want to alter UDP as well, you need to provide similar rules but with -p udp option set).

Last, but not least is routing configuration. Type:

ip route

and check if 192.168.1.0/24 is among returned routing entries.

Best Answer

Related Solutions

Iptables – Broadcast UDP over VPN

Linux – How to Port Forward with Iptables

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