[USRP-users] X310 MTU frame size issue

Louis Brown rfengr00 at me.com
Thu Oct 23 21:31:25 EDT 2014


Operating my X310 from a UHD source in GRC via 10GE yields a low MTU at startup:

-----------------------------------------------
linux; GNU C++ version 4.8.3 20140911 (Red Hat 4.8.3-7); Boost_105400; UHD_003.008.000-6-gbde8e9a3
-- X300 initialization sequence...
-- Determining maximum frame size... 2188 bytes.
UHD Warning:
    For this connection, UHD recommends a send frame size of at least 8000 for best
    performance, but your system's MTU will only allow 2188.
    This will negatively impact your maximum achievable sample rate.
-----------------------------------------------

My MTU for the 10GE interface is 9000 (verified with ifconfig), and when I run benchmark_rate it finds the correct MTU:

------------------------------------------------
./benchmark_rate --rx_rate 200E6 --args "addr=192.168.40.2"
linux; GNU C++ version 4.8.3 20140911 (Red Hat 4.8.3-7); Boost_105400; UHD_003.008.000-6-gbde8e9a3

Creating the usrp device with: addr=192.168.40.2...
-- X300 initialization sequence...
-- Determining maximum frame size... 8000 bytes.
-----------------------------------------------

So is this a GR issue or a UHD issue, or a combination?

Thanks,
Lou
KD4HSO
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