Many network administrators believe that changing from default RFC 1918 private IP ranges (like 192.168.1.0/24) to less common ranges (like 10.10.150.0/24) inherently improves security. While there's some truth to this, the actual security benefits are often misunderstood.

The primary risk with default IP ranges occurs in these specific scenarios:

• When devices have default credentials (admin/admin)
• When firewall rules are improperly configured
• During lateral movement after initial compromise

Example of a common scan pattern attackers use:

import nmap
scanner = nmap.PortScanner()
for i in range(1,255):
    ip = f"192.168.1.{i}"
    scanner.scan(ip, arguments='-T4 -F')
    if scanner[ip].state() == "up":
        print(f"Found active host: {ip}")

Behind a properly configured SonicWall (or any enterprise firewall), the internal IP scheme becomes largely irrelevant to external threats. The firewall's NAT translation and stateful inspection provide the actual security layer.

Custom ranges become valuable in these specific cases:

• Preventing accidental IP conflicts during VPN connections
• Reducing noise from internet-wide scans hitting your external interface
• Making internal reconnaissance slightly harder after initial breach

Example firewall rule that shows proper protection regardless of IP scheme:

# SonicWall equivalent CLI config
access-rule inside to outside
  source any 192.168.1.0/24
  destination any Internet
  service HTTP,HTTPS,SSH
  action allow
  log enabled
  exit

Instead of focusing solely on IP ranges, prioritize:

• Strict firewall rules with default-deny policies
• Network segmentation using VLANs
• Regular credential rotation
• Proper logging and monitoring

Example Python script to monitor suspicious internal scans (works with any IP range):

from scapy.all import sniff, IP, TCP

def detect_scans(pkt):
    if TCP in pkt and pkt[TCP].flags == 2:  # SYN scan detection
        src = pkt[IP].src
        dst = pkt[IP].dst
        if src.startswith(("192.168.1.", "10.10.150.")):
            print(f"Possible internal scan from {src} to {dst}")

sniff(prn=detect_scans, store=0)

Many network admins assume that using non-default IP ranges like 10.10.150.0/24 provides inherent security advantages over the common 192.168.1.0/24 range. While there's some truth to this, the reality is more nuanced.

Malicious actors often:

• Scan default subnets first when attempting lateral movement
• Use pre-built exploit tools targeting common home/office networks
• Assume default credentials might work on devices in these ranges

Example of a typical masscan command attackers might use:

masscan -p1-65535 192.168.1.0/24 --rate=10000

While changing from 192.168.1.x provides some security through obscurity, more critical factors include:

• Proper firewall rules (your SonicWall configuration)
• Network segmentation
• Regular patching
• Strong authentication mechanisms

For your SonicWall, consider these security enhancements regardless of IP scheme:

# Sample SonicOS CLI commands for improved security:
configure
security-management
    set ssh-access restricted
    set https-access internal-only
exit
access-rule
    add name="Block Internal Scans" action=deny src=lan-ip dst=lan-ip service=any log=yes
exit

Consider switching from default ranges when:

• Merging networks that might have conflicting ranges
• Implementing complex VLAN segmentation
• Deploying large-scale infrastructure where scanning is more likely

Implement network monitoring that doesn't rely on IP obscurity:

# Sample Suricata rule to detect internal scanning
alert (msg:"INTERNAL NETWORK SCAN DETECTED"; flow:to_server; 
    detection_filter:track by_src, count 50, seconds 10;
    sid:1000001; rev:1;)