When configuring a default gateway in a 192.168.100.0/24 subnet, network administrators typically choose between two conventional approaches:

Option 1: 192.168.100.1
Option 2: 192.168.100.254

The choice between first or last available IP involves several technical factors:

• Network Device Defaults: Most consumer routers default to .1 (e.g., Linksys, Netgear)
• Enterprise Convention: Many enterprises prefer .254 for easier identification
• DHCP Range Planning: Choosing .1 leaves .2-.253 for DHCP (253 addresses)
• Consistency: Matching existing infrastructure patterns

Here's how to set the gateway in Linux:

# For 192.168.100.1
sudo ip route add default via 192.168.100.1 dev eth0

# For 192.168.100.254
sudo ip route add default via 192.168.100.254 dev eth0

In Cisco IOS:

interface Vlan100
 ip address 192.168.100.1 255.255.255.0
!
ip route 0.0.0.0 0.0.0.0 192.168.100.254

After working with numerous networks, I recommend:

• Use .1 for small networks/SOHO environments
• Use .254 in enterprise environments with multiple VLANs
• Document your choice in network topology diagrams
• Keep DHCP ranges clearly separated from static assignments

In hypervisor setups, you might see different patterns:

# ESXi example using .253
esxcfg-route 192.168.100.253

This demonstrates that while .1 and .254 are common, other conventions exist depending on the specific technology stack.

In a typical 192.168.100.0/24 subnet, administrators commonly debate whether to use the first usable IP (192.168.100.1) or last usable IP (192.168.100.254) as the default gateway. Both approaches have valid technical justifications.

# Example network configuration using first IP
interface GigabitEthernet0/0
 ip address 192.168.100.1 255.255.255.0
 no shutdown

The first IP approach (.1) offers several advantages:

• Matches common convention in documentation and examples
• Easier to remember for non-technical staff
• Consistent with many vendor default configurations

# Alternative configuration using last IP
interface GigabitEthernet0/0
 ip address 192.168.100.254 255.255.255.0
 no shutdown

The last IP approach (.254) provides benefits like:

• Creates clear separation between gateway and client IPs
• Reduces chance of IP conflicts during DHCP assignment
• Follows some enterprise network design guidelines

For Cisco routers, the configuration would be:

# First IP gateway configuration
enable
configure terminal
interface vlan 100
 ip address 192.168.100.1 255.255.255.0
 no shutdown
exit
ip route 0.0.0.0 0.0.0.0 192.168.100.1

For Linux systems using netplan:

# Last IP gateway example
network:
  version: 2
  ethernets:
    eth0:
      addresses: [192.168.100.254/24]
      routes:
        - to: default
          via: 192.168.100.254

When using ISC DHCP server, the configuration differs based on gateway choice:

# Using first IP as gateway
subnet 192.168.100.0 netmask 255.255.255.0 {
  range 192.168.100.10 192.168.100.253;
  option routers 192.168.100.1;
  option domain-name-servers 8.8.8.8;
}

# Using last IP as gateway
subnet 192.168.100.0 netmask 255.255.255.0 {
  range 192.168.100.2 192.168.100.200;
  option routers 192.168.100.254;
  option domain-name-servers 8.8.8.8;
}

In larger networks, the choice may depend on:

• Existing corporate standards
• Security policies regarding IP address ranges
• Integration with VLAN design
• Automation tool compatibility

For Python network automation, you might handle it like:

def configure_gateway(use_first_ip=True):
    if use_first_ip:
        gateway_ip = "192.168.100.1"
        dhcp_range = ("192.168.100.10", "192.168.100.253")
    else:
        gateway_ip = "192.168.100.254"
        dhcp_range = ("192.168.100.2", "192.168.100.200")
    
    return {
        "gateway": gateway_ip,
        "dhcp_range": dhcp_range,
        "subnet": "192.168.100.0/24"
    }