How it works
Network debugging is layered
Confirm physical link, IP address, route and name resolution before tracing packet paths.
Use portable observations first
Network provider names can differ; syscall tracing and built-in network tools give a reliable first pass.
Avoid payload capture
Tracing network data can expose secrets. Aggregate metadata unless packet contents are essential and authorized.
Worked examples
Each example explains the question it answers, a reproducible starting point, what to look for, and operational precautions.
1. Count send and receive syscalls
Identify chatty processes.
syscall::send*:entry { @send[execname] = count(); }
syscall::recv*:entry { @recv[execname] = count(); }Interpretation: Probe wildcards match available syscall names; compare against `netstat -s`.
Operational note: Run commands in a test environment first; confirm device names, privileges and release-specific options.
2. Time connect attempts
Find slow outbound connection establishment.
syscall::connect:entry { self->t = timestamp; }
syscall::connect:return /self->t/
{
@connect_ns[execname] = quantize(timestamp-self->t);
self->t = 0;
}Interpretation: Latency includes syscall time; application-level connection readiness may extend beyond the return.
Operational note: Run commands in a test environment first; confirm device names, privileges and release-specific options.
3. Check IP state
Rule out ordinary configuration errors.
dladm show-phys
ipadm show-addr
netstat -rn
netstat -sInterpretation: Validate interface/link/route counters before interpreting DTrace output.
Operational note: Run commands in a test environment first; confirm device names, privileges and release-specific options.
Before you finish
- Use capture policies that protect user data and credentials.
Primary documentation
Read the relevant Oracle documentation for exact version-specific flags, supported platforms and limitations: Oracle primary reference ↗.
This field manual is independent, not affiliated with or endorsed by Oracle. Command examples should be adapted to your environment.