Port forwarding problems for Wake on Lan

An area specifically for port forwarding, firewalls and other (on-line) security related issues.
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Joined: Tue Jul 30, 2013 8:36 am

Port forwarding problems for Wake on Lan

Post by fbrighi » Tue Jul 30, 2013 9:21 am

I have a modem-router netgear Dgnd4000, and I have configured it to allow wake on lan of a Synology Ds212 Nas through internet. As from previous model I had (D-link), I did the following :

- I provided Nas with static ip on router
- I provided Arp table to keep permanently the association between previous set up static ip and Nas mac address. To do this, I used the comand "ip neigh add <IP number> lladdr <MAC number> dev group1", given by telnet connection.
- I forwarded the port 5000, for both TCP/UDP protocols, to the static ip

Even doing this, WOL from internet is not working. Also changing port for WOL (7 and 9, pure UDP protocol) nothing working. Using wireshark (and other tool to see if ports are open or not) I discovered that, even if forwarded, ports are considered always closed (when Nas is off). Despite of this, WOL starts to work only after I switched on the NAS and accessed it from internet (i use for this a Dynamic DNS service) at least one time. In fact, after shutting down the Nas, it can be powered on through internet wol. Doing so, and only using 5000 port (port 5000 corresponds to the one used by Dynamic DND to access in remote the Nas), I'am able to operate Wake on Lan through internet. The interesting thing is that this is possible only within few hours (approx 10 hours); after that time, again port 5000 become as it is "not open", and wol stops working.

I have the impression that router is not considering port open, even if forwarded, until it is not seeing "traffic" going thorugh it (i.e. when nas is accessed from internet) and it applies a kind of "inactivity time", after which it considers again the port as "closed".

I checked for safety Arp table association, it is always active and declared as permament.

Can anybody help me with this problem? Is there any command i can give from telnet to say to router that port 5000 (or 7, 9 ...) has to be considered always open?

Thank you and best regards,
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