Find_usrps only succeed when an sniffer is ON

GNU Radio
1

I installed GNU Radio on a ThinkPad Lenovo T4410 under Ubuntu 10.04.
After connecting the USRP2 with the original Ettus code on the SD card D
and
F LEDs are ok and when executed:

~$ sudo find_usrps
No USRP2 found.

I run wireshark or tcpdump to see what happens in my network and I got:

~$ sudo find_usrps
00:50:c2:85:35:a2 hw_rev = 0x0400

If I stop the sniffer, I get again:

~$ sudo find_usrps
No USRP2 found.

My problem is that ‘find_usrps’ only works when a sniffer is running.
How
can it be explained?

Jorge,

2

On 09/07/2010 04:43 AM, Jorge M. wrote:

00:50:c2:85:35:a2 hw_rev = 0x0400

When a sniffer is running, the ethernet interface is placed into
“promiscuous” mode in which all ethernet frames are processed and passed
up to higher layers in the networking stack. In non-promiscuous
mode, only frames that are addressed to the particular hosts ethernet
address, and the broadcast address, are forwarded up the stack.

My understanding is that find_usrps sends out a broadcast packet, and
the responding USRP2 replies using a broadcast packet, but even
in non-promiscuous mode, the hosts interface should pass the broadcast
traffic “upwards”. I wonder if there’s some interaction with
firewall rules at play here as well?

–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

3

Michael,

Thanks for your answer. My interface is completely ‘up’ after both
commands (promisc up and -promisc). But host computer and USRP2 can
only communicate when my network is in promiscuous mode.

I connect both, host computer and USRP2 through a direct connection
with a 1 Gb ethernet wire (no switches)

I only have one Ethernet interface in my host computer (eth0) and
permissions con /usr/bin/usrp2_socket_opener
are set to 4775.

I still cannot figure out what the problem is.

Jorge

00:50:c2:85:35:a2 hw_rev = 0x0400

If I stop the sniffer, I get again:

~$ sudo find_usrps
No USRP2 found.

My problem is that ‘find_usrps’ only works when a sniffer is running.
How can it be explained?

Jorge,