How to Capture Only Incoming Packets Using Wireshark Filters: A Technical Guide for Network Analysis


11 views

When working with Wireshark, it's crucial to distinguish between capture filters (BPF syntax) and display filters (Wireshark's own syntax). Capture filters operate at the kernel level during packet capture, while display filters work on already-captured data.

To capture only incoming packets, you'll need to use Berkeley Packet Filter (BPF) syntax in your capture filter. The most effective approach depends on your network configuration:


# For Ethernet interfaces (common case)
dst host [your_ip_address]

# Alternative for any destination on your interface
dst net [your_network]/[netmask]

Here are some concrete examples for different scenarios:


# Capture incoming traffic to specific host
dst host 192.168.1.100

# Capture incoming traffic to subnet
dst net 192.168.1.0/24

# Capture incoming traffic to multiple ports
dst port 80 or dst port 443

Regarding your side question about multiple files: Wireshark's ring buffer feature allows you to:

  • View complete packet information later
  • Navigate between files seamlessly
  • Search across multiple files

For more precise filtering, combine direction filters with protocol-specific ones:


# Incoming HTTP traffic
dst port 80 and tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x47455420

# Incoming DNS queries
dst port 53 and udp[10:1] & 0x80 = 0

Always test your filters with known traffic patterns. Use these methods:


# Generate test traffic
ping -c 1 [target_ip]  # Outbound test
nc -l -p [port]        # Inbound test listener

When analyzing network traffic, distinguishing between incoming and outgoing packets is crucial for security monitoring, troubleshooting, and performance analysis. Wireshark provides powerful filtering capabilities through BPF (Berkeley Packet Filter) syntax for capture-time filtering.

To capture only incoming traffic on an interface, use this BPF filter:

not src net [your_local_network]

For example, if your local network is 192.168.1.0/24:

not src net 192.168.1.0/24

For more precise control, consider these variations:

# Capture only incoming TCP traffic
tcp and not src net 192.168.1.0/24

# Capture incoming traffic from external hosts only
dst host [your_ip] and not src net 192.168.1.0/24

When logging to multiple files in Wireshark (using the "Use multiple files" option in Capture Options), you can later view complete packet information by:

  • Opening the specific file containing the packets you need
  • Using the File → Merge option to combine capture files
  • Ensuring "Merge chronologically" is checked for proper sequencing

To capture incoming HTTP requests while excluding local traffic:

tcp port 80 and not src net 192.168.1.0/24

This filter will capture all HTTP traffic destined for your web server from external sources.

Directional filtering at capture time significantly reduces:

  • Storage requirements for large captures
  • CPU usage during capture
  • Analysis time when reviewing packets

Always test your filters with known traffic patterns. Use these commands to generate test traffic:

# Outgoing test (should be excluded)
ping -c 1 google.com

# Incoming test (should be captured)
nmap -p 80 [your_ip_address]