By default, Nmap scans the 1,000 most common ports. But you can customize this with different options to scan fewer or more ports based on your goals.

This is useful for speeding up scans, checking only specific services, or performing full sweeps when needed.

--top-ports

Scans the top N most commonly used ports, based on a list of ports ranked by frequency of appearance across the internet.

nmap --top-ports=100 192.168.1.10

Key points

• Scans only the most popular ports
• Faster than default 1000-port scan
• Great for quick checks or large networks

-F (Fast Mode)

Scans only ports listed in Nmap’s “nmap-services” file (usually around 100). It’s a faster scan with less detail.

nmap -F 192.168.1.10

Key points

• Very fast scan
• Checks only common ports
• Good for initial sweeps or low-priority targets

-p- (Scan All 65,535 Ports)

Scans every single port from 1 to 65535. This is a full-range scan and takes more time.

nmap -p- 192.168.1.10

Key points

• Complete scan of all TCP ports
• Slower, more detailed
• Useful for deep audits or hidden services

-p (Manual Port Selection)

Lets you define specific ports, ranges, or combinations using a single option. This gives full control over what Nmap checks.

nmap -p 22 192.168.1.10          # Just port 22  
nmap -p 10-100 192.168.1.10      # Port range 10 to 100  
nmap -p 22,80,443 192.168.1.10   # Multiple specific ports  
nmap -p 1-100,443,8080 192.168.1.10  # Mixed range and values

Key points

• Choose any port or range
• Useful for targeting known services
• Great for scanning fast with precision

Port Scan Type Comparison

Option	What It Does	Speed	Customizable	Best For
--top-ports	Scans top N most common ports	Fast	Yes	Prioritizing popular services
-F	Fast scan of 100 common ports	Very Fast	No	Quick sweeps
-p-	Scans all 65,535 ports	Slow	No	Full deep scans
-p	Scan specific ports or ranges	Fast–Medium	Yes	Focused scans or known services