On 10/16/2018 09:58 AM, Lundberg, Daniel via USRP-users wrote:
I am following the N310 Getting Started Guide, which states to set
MTUBytes to 8000 for 1 GB on SFP0. If that is incorrect, perhaps the
guide should be updated?
https://kb.ettus.com/N300/N310_Getting_Started_Guides
MOST 1GiGe controllers will actually allow larger MTU. SOME (notably
certain RealTek) will happily accept a larger MTU via
the ethtool interface (on Linux) but silently still only process
1500-byte frames.
*From:*Ali Dormiani <sdorm...@eng.ucsd.edu>
*Sent:* Monday, October 15, 2018 7:21 PM
*To:* Lundberg, Daniel <daniel.lundb...@gtri.gatech.edu>
*Cc:* usrp-users <USRP-users@lists.ettus.com>
*Subject:* Re: [USRP-users] N310 MPMD link speed warnings
1 Gbe Ethernet can't handle that much data. Most 1 Gbe class NIC
controllers prevent you from setting the MTU over 1500 anyway. I would
be surprised if the GUI settings in network manager actually went
through. If you type 'ifconfig' in a command console the host NIC is
probably still running at 1500 MTU.
https://en.wikipedia.org/wiki/Ethernet_frame#Ethernet_II
The N310 supports two modes.
1. 1.25 Gbe mode
2. 10 Gbe mode
I think the warning is saying that it does not know what to do (link
negotiation with your host NIC failed) so it defaults to the slower of
the two modes.
On Mon, Oct 15, 2018 at 3:22 PM Lundberg, Daniel via USRP-users
<usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>> wrote:
I am using Ubuntu 18.04, an N310 with the current master builds.
I am currently testing basic operation using a USB/Ethernet
adaptor for the management connection, and a 1 GB Ethernet
connection straight from the computer’s NIC port to the SFP0 port
on the N310.
I have built from source and can make it through all of the
examples and benchmarking exercises successfully. I am also able
to successfully run the tx_waveform example with a streaming rate
of 25e6 with a master clock rate of 125e6. This seems to be the
limit, 31.25e6 causes underruns.
Despite the streaming link seeming to work, there are chronic
warnings such as:
“[WARNING] [MPMD] Could not determine link speed; using 1GibE max
speed of 125000000
The network connections were set up within Ubuntu’s network
manager, with MTUBytes = 8000 (also set in the N310’s
/etc/system/network/ files).
Autonegotiation is enabled on both ends, per ethtool outputs.
Any input on where these warnings originate, and if there is a way
to suppress them?
Thank you
Dan
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