Re: [Linuxptp-users] I am trying to get PTP to work over an interesting network topology.

[Richard C. <ric...@gm...>]

On Tue, May 26, 2015 at 03:29:01PM -0500, Robb wrote:
> I am having trouble getting PTP to work over a network bridge br0.

I have not tried PTP over a Linux SW bridge, and I am not sure if the
kernel stack will play along.  In my experience, Linux SW bridging is
a bit flakey.

(PTP *does* work over tun/tap, but only after I patched the kernel.)
 
> So what is the bridge messing up? And is there a way to fix it?

The default transport is multicast UDP.  Maybe the SW bridge is
dropping multicast.  Run wireshark on the end points to see if the PTP
messages are getting through.

> I would appreciate any insight I can get.  Even if it is a suggestion for a
> better topology.

One easy thing to try is Layer2 transport:

   ptp4l -i eth0 -m -q -2

This doesn't require the stack to join the multicast group, and so
maybe it will "just work."

HTH,
Richard