Dealiasing

Dealiasing reduces redundant follow-up probes by determining whether an IPv6 address belongs to a router interface that represents a larger prefix. rmap’s default engine performs extra fan-out probes behind the scenes and adds per-target metadata to every scan result.

Capture aliasing data during scans

rmap scan --path targets.txt --pps 1000 --timeout 6 icmp \
  --output-file reachability.csv \
  --columns target,alias,alias_prefix,latency_ms

The alias column records aliased, not_aliased, or unknown. When the address appears to be part of a larger interface, alias_prefix reports the estimated prefix length (typically /64).

Tips:

• Increase --timeout if you expect slower fan-out replies; the dealiaser uses the same timeout as the primary probe.
• Combine --unique with dealiasing when you are sampling large hitlists—it prevents the fan-out from repeatedly analysing identical targets.
• Include the alias column in dashboards or exports so downstream tools can filter out router interfaces automatically.

Post-processing ideas

• Pipe results into rmap analyze to compare entropy or dispersion between aliased and non-aliased targets.
• Use Python scripting (pip install pyrmap) to group results by alias_prefix and trigger deeper surveys only for unique addresses.
• When running remote scans, collect metrics per worker to ensure the aliasing rate stays stable across regions.