PTP Multicast Groups and Ports

The PTP protocol uses the following multicast addresses:

• 224.0.1.129
• 224.0.0.107

sfptpd will join these groups and periodically renew group interest using the IGMP protocol.

Use the Linux netstat -ng command or the following command to identify multicast groups joined on the sfptpd interface:

# cat /proc/net/igmp

Idx     Device    : Count Querier       Group    
1       lo        :     1      V3
                                010000E0   1   
2       eth0      :     1      V2
                                010000E0   1   
10      virbr0    :     1      V3
                                010000E0   1   
15      eth4      :     3      V2
                                6B0000E0   2   
                                810100E0   2   

81  01  00  E0      6B  00  00  E0
129  1   0  224     107  0   0  224

PTP only uses UDP ports 319 and 320. To capture only PTP traffic use tcpdump in the following format:

# tcpdump -i <sfptpd interface> dst port 319 or dst port 320 [-wptp.pcap]