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

[Robb <rba...@gm...>]

I attempted to enable UDP multicast by setting
net.ipv4.all.rp_filter = 0
in /etc/sysctrl.conf with no luck

However, I used your suggestion to use layer 2 and it did "just work"
which is really nice.  It is also really refreshing to see a mailing list
responded to so quickly, and with such accurate and helpful information.

Thank you very much.

-Robb





On Tue, May 26, 2015 at 3:53 PM, Richard Cochran
<ric...@gm...> wrote:
> 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