This project is read-only.

WAN emulation

Sep 20, 2012 at 3:18 AM



I have just discovered your project, and I think it is great! But I find it difficult to use, as there are too few examples.


I was just wondering how the Wan Emulator works. I have configured an interface attached to a router, and then the router tx/rx connected to the Wan emulator tx/rx. I have setup up probability of packets loss to 100%, but nothing happens. Could you please provide some advice?



Sep 20, 2012 at 5:13 PM


thank you for your kind words. :).
I know there are fery few examples, but I am here for support.

Here is an article concerning the WAN emulator:

In general, Net Lab can only affect the traffic of other devices, which is being routed by the computer on which Net Lab is running, but not the traffic of the computer which is running Net Lab (due to technical restrictions).
It is, for example, possible to constrain the traffic flow of other devices on the local network to the gateway, or between two hosts or routers in a lab environment.

  • The first step is to set up routing, either between two interfaces or using only one interface. This can be done by linking the interfaces to a router, connecting the router to the WAN emulator like you probably already did. For routing, also adjustments to the routing table of the router could be necessary.
    An alternative to this step is to use the direct Interface I/O, but in this case you will need two network interfaces.
  • Then, you have to assure the routing is working. Try to access the destination and ensure that the traffic flows over the Net Lab instance. Try to ping between the two hosts and use the traffic dumper or the rx/tx signals of Net Lab to check. The other devices may need an altered IP configuration (with your Net Lab host as gateway). You can also choose to intercept the traffic via ARP Poisoning (With the ARP spoofer).
  • As soon as the traffic flows through Net Lab, it is possible to use the WAN emulator. Packet loss of 100% would drop all traffic.

If you give me some idea of what you are trying to do (and how your network environment is configured), I could give you some suggestions regarding the steps above, since there are many ways of modifying traffic, and some fit better than others.

Sep 20, 2012 at 6:25 PM

Hi emiswelt,

Thank you for your quick response!!

First I would like to know what are the technical restrictions for not affecting the traffic on the running computer. Do you mean the outbound traffic, the inbound or both?

But I want to do is just what your software seems to achieve, which is emulate packet loss, bandwith limit, etc. when you choose one adapter, and to see the effect on the same computer where the software is executing.

Actually, I don´t understand well then how you can affect other computers traffic but not the one running the software. So let´s say you have an adapter, setup a router in the software, and then a wan emulator.
If you do not add routing tables to the router, then it does not do anything? If your computer is let´s say with gateway, and there is another computer in your LAN (let´s say 136), which is the routing configuration for seeing the emulation effect in when comunicating with, or when comunicating with the rest of PCs in the LAN or with WAN?

I hope that I have explained my doubts correctly so that you can understand my goals.

Thank you very much again for your time!


Sep 20, 2012 at 11:53 PM


The problem with traffic of the host running Net Lab is that it is not possible to change it at the moment. You can analyze your own traffic (inbound and outbound), but it is not possible to intercept and change it before sending it out to the network or passing it up to the operation system. Traffic which is sent by other hosts and forwarded by Net Lab to it's desintation can be modified.

A router without extra entries in the routing table (default entries for the interface are added automatically) does only route between networks which are directly connected. For routing to a gateway to the internet, add a so known default route to the router. Set destination to, subnet mask to, next hop to your gateway address and metric to 10. This will ensure all traffic which is not addressed for the local network will be forwarded to your gateway, which sends it out to the internet. Also uncheck "Exclude Traffic from/to local host" in the interface settings panel for routing.

The only thing you have to do now is to ensure the other computer ( is using the computer running Net Lab ( as gateway. You can accomplish this pretty easy by changing the IP configuration of

Now the traffic from to the internet is sent to your computer running Net Lab, processed there, and then send to your gateway which forwards the packets to the internet. Other hosts in the network or communication between two hosts on the network are not affected.

You can test this by setting the packet loss to 50% and trying to ping a server on the internet from


Oct 7, 2012 at 11:07 PM

Hi Vedder,

Has your issue been resolved?

Best regards

Oct 11, 2012 at 8:45 AM

Hi emiswelt!

To tell you the truth, I have had no more time to play with the application, but I think it is really really cool. When I have some time in the future I would like to review it again, and be back to you for more comments.


Many thanks!!