Datapath Packet-Trace & FIA-Trace

The Packet-Trace feature provides insight into how packets are processed through the hardware and software data paths on Cisco platforms. It is a powerful diagnostic tool that can be used in production environments without severely impacting performance.

Packet Trace allows inspection of packet handling using three levels of granularity:

Packet-Trace Levels

Level	Description
Accounting	Lightweight and runs continuously. Provides a count of packets entering and leaving the network processor. Minimal impact on performance.
Summary	Tracks input/output interfaces, packet state, and whether it was punted, dropped, or injected. Higher resource usage than accounting. Useful for identifying problem interfaces.
Path data	Provides the highest level of detail, including timestamps, debug IDs, and feature-specific processing data. Optional enhancements include packet-copy and Feature Invocation Array (FIA) tracing. Highest performance impact and should be used with care.

Note: Path data collection is resource intensive. Use sparingly in live environments where performance is critical.

Guidelines and Memory Considerations

• Use ingress condition filters to limit scope and avoid performance degradation.
• Packet trace consumes data-plane memory. The memory usage is estimated by:

memory required = statistics_overhead + number_of_packets * (summary_size + data_size + packet_copy_size)

Configuration Steps

Creating a Path Trace

c8000v-0# debug platform packet-trace ?
  copy        Copy packet data
  drop        Trace drops only
  inject      Trace injects only
  packet      Packet count
  punt        Trace punts only
  statistics  enable packet trace statistics

debug platform packet-trace packets 2048 fia-trace circular

You can enable multiple types of data being collected, as seen above.

Apply Match Conditions

You can limit the packet trace to specific interfaces or traffic flows.

Example: Match on ingress interface

debug platform condition interface g0/0/0 ingress

Example: Match on source IP

debug platform condition ipv4 192.168.1.1 ingress

Combine multiple conditions to narrow down further.

Start and Stop Packet Trace

debug platform condition start
...
debug platform condition stop

View Packet Trace Data

show platform packet-trace configuration
show platform packet-trace statistics
show platform packet-trace summary
show platform packet-trace packet all

Clear All Conditions

clear platform condition all
clear platform packet-trace configuration

Example Workflow

debug platform packet-trace packets 100 fia-trace circular
debug platform packet-trace statistics
debug platform condition interface GigabitEthernet0/0/0 egress

show platform packet-trace configuration
show platform condition

debug platform condition start

...generate test traffic...

debug platform condition stop
show platform packet-trace summary
show platform packet-trace statistics
show platform packet-trace packet #

...cleanup when done...

clear platform condition all
clear platform packet-trace configuration

Reference

Cisco Packet Trace Configuration Guide