[Linuxptp-users] LinuxPTP in unicast

[Marco D. (SIDN) <mar...@si...>]

Hi,

I created a unicast setup. It was an experiment to verify if I could 
make my PTP-service more resilient against 'rogue' masters on the same 
VLAN that (falsy) claim to be the best master.

The setup works fine. However, I noticed that when the real (unicast) 
master(s) become(s) unavailable, the slave is still sensitive to 
multicast packages. So, when a 'roque' master is transmitting via 
multicast, the slave will sync to it. That is precisely what I was 
hoping to prevent, so I was surprised.

Disabling multicast on the ethernet interface isn't a trivial thing to 
do ("ifconfig eth0 -multicast" has no effect), so I solved it by 
blocking port 319/320 multicast with iptables.

But I was wondering; isn't it a bit strange for ptp4l to pick up 
multicast packets, even when it is configured to do unicast?

Is this a bug or a feature?

-- 
Marco