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Re: [Discuss-gnuradio] TunTap Interace for GNU Radio IEEE 802.11 a/g/p m

From: Bastian Bloessl
Subject: Re: [Discuss-gnuradio] TunTap Interace for GNU Radio IEEE 802.11 a/g/p module
Date: Fri, 3 Feb 2017 22:22:44 +0100


On 3 Feb 2017, at 21:41, Qurat-Ul-Ann Akbar <address@hidden> wrote:


I am trying to run the transceiver which has a tuntap pdu block for sending messages through TCP. There is a bash file nic.sh which gives an example configuration for the tuntap interface. 

I am not very familiar with working with tuntap and trying to understand it. Can anyone kindly tell me if the MAC address you set for the tuntap interface is random?

It’s just any value. In the example setup I configure static ARP entries (i.e., on another device I would add an ARP entry that maps the IP of the TUN/TAP devices to the MAC address that I set here.

Or is there a particular logic behind setting to a particular value. Also should its IP address be in the same subnet of the Ethernet interface the USRP device is connected to?

No that doesn’t have anything todo with each other. In fact, that would make it more complicated.Use different subnets for the USRP and the WiFi/SDR communication.

(in my case the IP of the Ethernet interface is and mask is /24) And can it be anything in

If you USRP is not in that subnet, everything is fine.

In the file nic.sh the MAC address of the tap0 interface is set to 12:34:56:78:90:ab and the IP address is

And then the arp command is used to map to the MAC address 30:14:4a:e6:46:e4.

How does this interface end up sending messages through the USRP? 

If the IP stacks has a packet for a host that’s in the subnet of the TUN/TAP interface, it puts the packet in the TUN/TAP interface. With this, the packet ends up in GNU Radio, which constructs a WiFi frame out of the Ethernet frame (finally it creates some IQ samples) and sends it to the USRP. (In your case the USRP is also connected via IP, but that’s a totally unrelated network).


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