How to switch Datgram/Connected mtu modes?

Alex Liptsin alexl at
Tue Jun 11 07:05:23 UTC 2013


Yes. There is no such entry.
The only way I found is to compile inside the kernel " options IPOIB_CM ".
Can I do it manually without compiling the kernel each time I want to switch between the modes?
Maybe add it somehow to sysctl or loader.conf?

Alex Liptsin
Software Quality Assurance Engineer | Mellanox Technologies Ltd.
Office: +972 (74) 7236141
Mobile: +972(54) 7833986
Fax: +972(74) 7236161 
Email: alexl at
Mellanox, Tel-Hai Industrial Park. Building 7, M.P. Upper Galilee 12100 Israel

-----Original Message-----
From: John Baldwin [mailto:jhb at] 
Sent: Wednesday, May 29, 2013 9:17 PM
To: freebsd-net at
Cc: Alex Liptsin; freebsd-questions at
Subject: Re: How to switch Datgram/Connected mtu modes?

On Sunday, May 26, 2013 7:43:29 am Alex Liptsin wrote:
> Hello.
> I work with FreeBSD 9.1 and Mellanox devices.
> How can I configure MTU in connected mode on FreeBSD 9.1?
> In Linux to enable connected mode for interface ib0, I enter:
>    echo connected > /sys/class/net/ib0/mode
> Switching between CM and UD mode can be done in run time:
>    echo datagram > /sys/class/net/ib0/mode sets the mode of ib0 to UD
>    echo connected > /sys/class/net/ib0/mode sets the mode ib0 to CM
> There is no such directories at FreeBSD. Wat shall I do?

Have you tried looking for dev.ib.0 sysctls?  It looks like the OFED bits in FreeBSD map Linux sysfs entries to sysctl nodes, but I don't have a box with IB handy to see what it looks like at runtime.

John Baldwin

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