GNS3 Packet Capture

Start and stop packet captures on links in GNS3 projects. Capture network traffic for analysis and troubleshooting.

When to Use

• Troubleshooting network connectivity issues in a lab
• Capturing traffic for analysis with Wireshark
• Verifying routing protocol exchanges (OSPF, BGP, etc.)
• Debugging application traffic
• Learning about network protocols
• Validating QoS or security policies

MCP Server

• Command: python3 -u mcp-servers/gns3-mcp-server/gns3_mcp_server.py (stdio transport)
• Requires: GNS3_URL, GNS3_USER, GNS3_PASSWORD environment variables

Available Tools

| Tool | Parameters | What It Does | |------|------------|--------------| | gns3_start_capture | project_id, link_id, capture_file_name? | Start packet capture on a link | | gns3_stop_capture | project_id, link_id | Stop packet capture and finalize PCAP file | | gns3_get_capture | project_id, link_id | Get capture file path and stream URL |

Workflow Examples

Capture Traffic for Analysis

bash
# First, identify the link to capture
"List all links in routing-test"

# Start capture on the link between router1 and router2
"Start capturing traffic on link abc123 in routing-test"

# Generate some traffic (ping, routing updates, etc.)
# ...

# Stop capture when done
"Stop the capture on link abc123 in routing-test"

# Get the PCAP file location
"Get capture info for link abc123 in routing-test"

Custom Capture Filename

bash
# Start capture with custom filename
"Start capturing on link abc123 in routing-test as ospf_adjacency.pcap"

Live Streaming

bash
# Get stream URL for live capture viewing
"Get capture info for link abc123 in routing-test"
# Returns stream_url for live PCAP streaming

Integration with Other Skills

• gns3-link-management: List links to find the one to capture
• gns3-node-operations: Ensure nodes are running before capturing
• packet-analysis: Hand off PCAP data for deep inspection

Capture Output

• PCAP Format: Standard libpcap format compatible with Wireshark
• File Location: Stored on GNS3 server, path returned in response
• Stream URL: Available for live capture viewing when capture is active

Error Handling

| Error Code | Meaning | Resolution | |------------|---------|------------| | GNS3_NOT_FOUND | Link doesn't exist | Use gns3_list_links to find valid link IDs | | GNS3_CONFLICT | Capture already running | Stop existing capture first |

Tips

1. Find the right link: Use gns3_list_links to see all connections and their IDs
2. Start before traffic: Begin capture before generating the traffic you want to analyze
3. Stop cleanly: Always stop capture to finalize the PCAP file
4. Use custom names: Descriptive filenames help organize multiple captures

Notes

• Captures are stored on the GNS3 server
• Link IDs are UUIDs from gns3_list_links
• Only one capture per link at a time
• Stop capture to ensure PCAP file is complete
• All operations logged to GAIT audit trail