RFC 1918 defines three sacred private address blocks that every network engineer should engrave in their memory:

10.0.0.0/8 (16,777,216 hosts)
172.16.0.0/12 (1,048,576 hosts)
192.168.0.0/16 (65,536 hosts)

The eternal debate between network purists and pragmatists:

• Round Subnet Zealots: "Stick to /8, /16, /24 boundaries for clean binary divisions"
• CIDR Realists: "VLSM all the way - waste no addresses!"

Religious wars over gateway placement:

# Traditionalists
interface VLAN10
 ip address 192.168.1.1 255.255.255.0

# Radicals
interface VLAN20
 ip address 10.0.42.254 255.255.255.0

# Heretics
interface VLAN30
 ip address 172.16.23.187 255.255.255.0

Sample Python code for systematic IP assignment:

def generate_ip_pool(subnet, reserved=20):
    """Generate IP addresses excluding network/broadcast and reserved range"""
    network = ipaddress.IPv4Network(subnet)
    hosts = list(network.hosts())
    
    # Reserve first N for infrastructure
    infrastructure = hosts[:reserved]
    user_pool = hosts[reserved:]
    
    return {
        'gateway': infrastructure[0],
        'dns_servers': infrastructure[1:3],
        'user_pool': user_pool
    }

# Usage
print(generate_ip_pool('192.168.1.0/24'))

Example DHCP reservation config (ISC DHCPd):

subnet 10.42.0.0 netmask 255.255.0.0 {
    range 10.42.1.100 10.42.1.200;
    option routers 10.42.0.1;
    
    host webserver {
        hardware ethernet 00:1a:2b:3c:4d:5e;
        fixed-address 10.42.0.10;
    }
    
    host printer {
        hardware ethernet 00:1b:3c:4d:5e:6f;
        fixed-address 10.42.0.20;
    }
}

When designing IPv4 subnets today, always consider:

• Dual-stack implementation possibilities
• Future renumbering to IPv6
• NAT64/DNS64 requirements

When architecting private networks, we operate within three sanctioned ranges:

10.0.0.0/8 (16,777,216 hosts)
172.16.0.0/12 (1,048,576 hosts) 
192.168.0.0/16 (65,536 hosts)

Consider these approaches for subnet allocation:

• Minimalist: /24 for small offices (254 hosts)
• Moderate: /23 for department VLANs (510 hosts)
• Future-proof: /22 for dynamic environments (1022 hosts)

# Example subnet calculation
$ ipcalc 10.42.0.0/22
Address:   10.42.0.0           
Netmask:   255.255.252.0 = 22  
Wildcard:  0.0.3.255           
Network:   10.42.0.0/22        
HostMin:   10.42.0.1           
HostMax:   10.42.3.254         
Broadcast: 10.42.3.255         
Hosts/Net: 1022

Common gateway placement conventions:

# Conservative approach
gateway = network_address + 1 (e.g., 192.168.1.1)

# Alternative scheme
gateway = broadcast_address - 1 (e.g., 192.168.1.254)

# Infrastructure devices often occupy lower ranges:
- .1 to .9: Network equipment (routers, switches)
- .10 to .19: Servers and critical services
- .20 to .199: DHCP pool
- .200 to .254: Static assignments

Best practice hybrid approach:

# Sample DHCPd configuration for mixed environment
subnet 10.100.20.0 netmask 255.255.255.0 {
    range 10.100.20.50 10.100.20.199;
    option routers 10.100.20.1;
    option domain-name-servers 10.100.20.2, 10.100.20.3;
    
    # Static reservations
    host webserver {
        hardware ethernet 00:1a:2b:3c:4d:5e;
        fixed-address 10.100.20.10;
    }
    host printer {
        hardware ethernet 00:1b:2a:3d:4e:5f;
        fixed-address 10.100.20.201;
    }
}

While waiting for full IPv6 adoption:

# Dual-stack configuration example
interface GigabitEthernet0/1
 ip address 10.55.77.1 255.255.255.0
 ipv6 address 2001:db8:cafe:55::1/64
 ipv6 nd managed-config-flag
 ipv6 dhcp server LAN_POOL

Always maintain an IPAM (IP Address Management) system:

# Example Ansible inventory with network metadata
[web_servers]
web01 ansible_host=10.20.30.41 vlan=30 role=frontend
web02 ansible_host=10.20.30.42 vlan=30 role=backend

[network_devices:children]
routers
switches

[routers]
core01 ansible_host=10.20.1.1 device_type=cisco_ios

[switches]
access01 ansible_host=10.20.1.11 device_type=cisco_ios