When you need to inventory devices on a network, there are several technical approaches depending on your access level and tools available. The most common methods include:

• ARP scanning (Layer 2 discovery)
• ICMP ping sweeps
• Port scanning techniques
• DHCP server interrogation
• SNMP queries (for managed networks)

For basic discovery in *nix environments, these commands can quickly reveal devices:

# ARP scan (requires root)
sudo arp-scan -l

# Ping sweep example (Linux)
for ip in $(seq 1 254); do ping -c 1 192.168.1.$ip | grep "bytes from"; done

# Windows alternative
for /L %i in (1,1,254) do @ping -n 1 -w 100 192.168.1.%i | find "Reply"

Here's a more sophisticated Python script using scapy:

from scapy.all import ARP, Ether, srp

def scan_network(ip_range):
    arp = ARP(pdst=ip_range)
    ether = Ether(dst="ff:ff:ff:ff:ff:ff")
    packet = ether/arp
    
    result = srp(packet, timeout=3, verbose=0)[0]
    
    devices = []
    for sent, received in result:
        devices.append({'ip': received.psrc, 'mac': received.hwsrc})
    
    return devices

print(scan_network("192.168.1.0/24"))

For professional network analysis, consider these tools:

• Nmap: Comprehensive network mapping tool

  nmap -sn 192.168.1.0/24

• Angry IP Scanner: GUI-based cross-platform scanner
• Fing: Mobile network discovery app

To detect devices with static IPs that might not respond to normal discovery:

1. Scan the entire subnet range

   nmap -T4 -A -v -PE -PS22,25,80 -PA21,23,80,3389 192.168.1.0/24

2. Compare ARP cache with DHCP leases
3. Check switch MAC address tables (if you have access)

When you need to find the default gateway/router:

# Linux/Unix
ip route show | grep default

# Windows
ipconfig | findstr "Default Gateway"

# Cross-platform alternative
traceroute -m 3 8.8.8.8 | head -n 2 | tail -n 1

Understanding connected devices requires two fundamental approaches: active scanning (sending packets) and passive monitoring (analyzing network traffic). For most programmers, active scanning provides immediate results with minimal setup.

The Address Resolution Protocol cache reveals devices on your local subnet. This Python example uses scapy:

from scapy.all import arping
result = arping("192.168.1.0/24")
result.show()

For Linux systems, the arp-scan utility provides detailed output:

arp-scan --localnet --interface=eth0

This method works across subnets but may be blocked by firewalls. Python implementation:

import subprocess
for ping in range(1,255):
    address = "192.168.1." + str(ping)
    res = subprocess.call(['ping', '-c', '1', '-W', '1', address])
    if res == 0: 
        print("Active: " + address)

For enterprise environments, querying the DHCP server provides authoritative data. Cisco IOS example:

show ip dhcp binding
show ip dhcp server statistics

When you have read community strings, SNMP reveals comprehensive device information:

snmpwalk -v2c -c public 192.168.1.1 1.3.6.1.2.1.4.22.1.2

Direct router access provides the most accurate device list. Common vendor commands:

# Cisco
show mac address-table
show arp

# MikroTik
ip arp print

For stealthy detection, analyze network traffic patterns with tools like p0f:

p0f -i eth0 -o fingerprint.log

Always obtain proper authorization before scanning networks. Many organizations monitor for scanning activity as potential security threats.