SUBNET MASK AND DEFAULT GATEWAY

SUBNET MASK

• Think of IP address as your house number in a big city.
• The subnet mask decides which part of the IP is the “area/street” and which part is the “house number”.

Example:
IP Address: 192.168.1.25
Subnet Mask: 255.255.255.0

• 255 means “fixed area” (network part).
• 0 means “house number can change” (host part).

So here:

• 192.168.1 = Network (street)
• .25 = Host (house)

With 255.255.255.0, you can have 254 devices (from .1 to .254) in that network.

DEFAULT GATEWAY

• The default gateway is like the main gate of your colony.
• Inside the colony, houses talk directly.
• But if you want to go outside the colony (different network), you need to go through the main gate (router).

Example:

• Your PC: 192.168.1.25
• Friend’s PC (same network): 192.168.1.50 → talk directly.
• Want to reach Google (142.250.183.206)?
  → Your PC sends data to the default gateway (e.g., 192.168.1.1),
  → The gateway then takes it outside to the internet.

In short:

• Subnet Mask = Splits the IP into network part vs device part.
• Default Gateway = The exit point (router IP) to talk to outside networks (like the internet).