# Issue with tuntap\_pdu **URL:** \ **Category:** GNU Radio\ **Created:** [November 7, 2014, 12:42am UTC](https://www.ruby-forum.com/t/issue-with-tuntap-pdu/232957 "2014-11-07T00:42:25Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [November 7, 2014, 12:42am UTC](https://www.ruby-forum.com/t/issue-with-tuntap-pdu/232957/1 "2014-11-07T00:42:25Z")
I am trying to run the example simple\_trx.py script from the gr-mac module and I am having an issue related to what I believe is gr::blocks::tuntap\_pdu. This is what I am doing. I open up a couple of terminal windows and in two of them I place in these separate commands. [root@xxxx project]# ./simple\_trx.py --radio-addr 85 --dest-addr 86 –port 12345 -a addr=10.2.8.104 [root@xxxx project]# ./simple\_trx.py --radio-addr 86 --dest-addr 85 –port 12346 -a addr=10.2.8.105 The former will run just fine and then the second one gives me this error [root@xxxx project]# ./simple\_trx.py --radio-addr 86 --dest-addr 85 –port 12346 -a addr=10.2.8.105 linux; GNU C++ version 4.4.7 20120313 (Red Hat 4.4.7-4); Boost\_104100; UHD\_003.007.001-64-g92b0b7ab libGL error: failed to load driver: nouveau libGL error: Try again with LIBGL\_DEBUG=verbose for more details. Using Volk machine: sse4\_2\_64 Simple MAC ARQ in non-blocking mode \ MTU: 128 ‘post\_msg’ not found. Using ‘message\_port\_pub’ instead. Virtual channel encoder in non-blocking mode \ MTU: 128 ‘post\_msg’ not found. Using ‘message\_port\_pub’ instead. Virtual channel encoder in non-blocking mode – Opening a USRP2/N-Series device… – Current recv frame size: 1472 bytes – Current send frame size: 1472 bytes – Detecting internal GPSDO… Found an internal GPSDO – found – Setting references to the internal GPSDO – Initializing time to the internal GPSDO \ tag name: length, multiplier: 32.000000, tag front: 0, tag rear: 16, drop residue: yes, verbose: yes bits per symbol = 1 M&M clock recovery omega = 4.000000 M&M clock recovery gain mu = 0.175000 M&M clock recovery mu = 0.500000 M&M clock recovery omega rel. limit = 0.005000 frequency error = 0.000000 Traceback (most recent call last): File “./simple\_trx.py”, line 386, in tb = simple\_trx(args=options.args, tx\_lo\_offset=options.tx\_lo\_offset, rx\_lo\_offset=options.rx\_lo\_offset, rate=options.rate, rx\_antenna=options.rx\_antenna, rx\_freq=options.rx\_freq, tx\_freq=options.tx\_freq, rx\_gain=options.rx\_gain, tx\_gain=options.tx\_gain, samps\_per\_sym=options.samps\_per\_sym, ampl=options.ampl, arq\_timeout=options.arq\_timeout, dest\_addr=options.dest\_addr, max\_arq\_attempts=options.max\_arq\_attempts, radio\_addr=options.radio\_addr, iface=options.iface, mtu=options.mtu, port=options.port) File “./simple\_trx.py”, line 157, in **init** self.blocks\_tuntap\_pdu\_0 = blocks.tuntap\_pdu(iface, mtu\*0 + 1514) File “/usr/local/lib64/python2.6/site-packages/gnuradio/blocks/blocks\_swig5.py”, line 1796, in make return \_blocks\_swig5.tuntap\_pdu\_make(\*args, \*\*kwargs) RuntimeError: gr::tuntap\_pdu::make: tun\_alloc failed (are you running as root?) Of course I am running this as root. Why can’t I have two instances of this running? Jonathan F. ---
**Author:** ![jfaulkenberry](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/c2a13f/32.png) [@jfaulkenberry](https://www.ruby-forum.com/u/jfaulkenberry)\ **Post date:** [November 10, 2014, 6:08pm UTC](https://www.ruby-forum.com/t/issue-with-tuntap-pdu/232957/2 "2014-11-10T18:08:23Z")
On Thu, Nov 6, 2014 at 6:41 PM, Jonathan F. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > –port 12345 -a addr=10.2.8.104 > > – Opening a USRP2/N-Series device… > M&M clock recovery gain mu = 0.175000 > arq\_timeout=options.arq\_timeout, dest\_addr=options.dest\_addr, > > Of course I am running this as root. Why can’t I have two instances of > this running? > > Jonathan F. Alright figured out my issue. I needed to specify a different interface for the second instance of simple\_trx so I couldn’t let it default to “tun0” so I specified it as “tun1”. Jonathan F.