Tcpdump Packet Capture

Enhanced PTP User Guide (UG1602)

Document ID
UG1602
Release Date
2022-10-18
Revision
1.0 English

Packet capture applications such as tcpdump can be useful to:

  • Identify if any PTP messages are actually being received on the PTP interface.
  • Identify if messages reported missing by sfptpd are actually being received at the PTP interface.
  • To inspect individual fields in PTP messages.

The following example shows how to use tcpdump to capture only PTP traffic.

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

where the <interface> is the network adapter interface being used by sfptpd.

Keep pcap files as small as possible, but large enough to capture an instance of the issue sfptpd is experiencing.

Note: tcpdump captures packets sent/received on an interface, but these packets might be not be delivered to the sfptpd daemon when they are prevented by other factors such as iptables rules, firewalls or reverse-path filters.