I setup a gateway to gateway vpn connection with linksys RV042 router. i was able to ping each other, access file sharing ( with netbios enabled ).

They are having same subnet mask, <--->

Firewall disabled.

But when i created/host LAN games (eg. warcraft3), it cannot be detect by clients at another site/LAN.

As i know warcraft3 is using UDP broadcast to tell the client the game is creaetd. 1. How to broadcast UDP to another LAN ? any things to do with multicast ?

  • 1 is not on the same subnet as – Zoredache Jun 30 '10 at 18:58
  • if not mistaken, if you having different subnet mask / you may require advance routing – user47221 Jul 1 '10 at 17:19
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    I don't mean to be rude but you need to know more about IP and Ethernet; whilst isn't an entirely invalid NM is isn't a valid one either. What you have created is two subneta with a tunnel between them and some basic L3 routing, what you wish to achieve is either a spanned VLAN or some form of UDP broadcast relay/helper similar to a DHCP helper. – Chopper3 Jul 1 '10 at 17:33
  • @user47221, what does that have to do with anything? Please see serverfault.com/questions/49765/… to learn about subnets. – Zoredache Jul 1 '10 at 17:37
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    No broacast is supposed to cross router oboundaries, VPN or not. Otherwise every idiot's broaedcasts would propagate through the whole internet. – TomTom Oct 6 '10 at 18:27

You may try to use UDP Broadcast Relay Utility


  • 2017 now and even though this hasn't seen any dev since 2013, it compiles and works very well! VERY simple to use also. Relay port 5555 to eth1: sudo ./udp-broadcast-relay -d 1 5555 eth1 – Jerther Apr 20 '17 at 13:11

I'm going to go out on a limb here and guess that you're an internet cafe, and that's why this is professional.

LAN games are usually designed to run on a LAN. You've set up your VPN using internetworking techniques, and to put it simply, the game treats this much the same way as the internet in general. The broadcasts it needs, and any non-IP protocols it might want to use, cannot cross the VPN link because they are not routeable. This is by design. They tend to rely on broadcasts (and, for older ones, things like IPX/SPX, which is not IP at all), and a lot of the reason for having separate subnets in the first place (as you have done; each side of your VPN is a different subnet) is to prevent this traffic from crossing certain boundaries.

At risk of greatly increasing your broadcast domains (this negatively impacts scalability), you should set up a layer 2 bridge instead of a routed VPN. Your hardware might support this or it might not, but it is the correct solution. This type of connection between two otherwise separate networks typically uses a protocol such as L2TP, and relays pretty much all the traffic (IP or otherwise, broadcast or unicast) that exists on the wire at one site to the wire at another site. In this way, instead of being two separate connected networks, the networks appear to be one LAN for all intents and purposes.

If you do this and you have a lot of hosts with a lot of broadcast traffic you don't care about (such as Windows NetBIOS stuff), you should consider using a firewall in addition to a layer 2 bridge to drop some of it. This is a non-security application of a firewall, but is useful to limit the amount of spurious broadcast traffic, thereby limiting the impact of large broadcast domains).


most routers by default don't allow broadcasts Chopper is on the right path, your VPN tunnel is up and running and appears to allow 'traffic', but you may need a 'helper' command, normally used to allow DHCP broadcast to cross a router. but i'm unfamiliar w/your router and thus you may also need to add a 'rule' at each end ie. route specific interface

and again use this routing command on the other router as well but routing the other way

route specific interface

essentially allow 'this network' 'this subnet' 'go to here'

note: using a reverse subnet mask, but your router may want the mask as

  • That is very much not what a static route does, and it isn't the correct solution in this case. Also, the usual way of allowing DHCP to cross between subnets is to use a DHCP relay. – Falcon Momot Aug 17 '13 at 19:19

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