prerquirements
overview
subnet (short for “subnetwork”) is a logical division of an IP address space.
It allows you to split a larger IP range into smaller, more manageable networks.
IP주소를 논리적으로 나눈 공간
많은 IP대역을 작게 분할해 여러 네트워크로 나누기 관리하기 위함
benefits
- better network:
- 네트워크를 보다 세밀하게 제어할 수 있음
- 낭비를 방지할 수 있음
- Improved Performance:
- Reduces broadcast domains (broadcast messages are only sent within the subnet)
- Can improve overall network performance
- Enhanced Security:
- Easier to implement firewalls and security policies at the subnet level
- Can isolate sensitive networks from others
- Scalability:
- Subnets can be sized according to specific needs (e.g., small office vs large data center)
disadvantages
- overhead: 사용할 수 있는 IP갯수가 줄어듦 (나눠)
사용할 수 있는 IP갯수가 줄어듦 (나눠진 서브넷 속에서 네트워크 주소, 브로드캐스팅에 대한 대역은 쓸 수 없으므로) - subnetting을 하면 할수록(네트워크를 나눌수록)
How It Works
For example, using a /24 subnet mask:
Network: 192.168.1.0/24
Broadcast: 192.168.1.255
Usable IPs: 192.168.1.1 - 192.168.1.254 (254 usable hosts)
Config Example
Here’s a typical subnet configuration:
# Router interface IP
interface GigabitEthernet0/1:
ip address 192.168.1.1 255.255.255.0
# Hosts on this subnet would have IPs like:
HostA: 192.168.1.2
HostB: 192.168.1.3
Characteristics
- Hierarchical Structure: Subnets can be further divided into smaller subnets if needed
- Broadcast Domain: All devices in a subnet are part of the same broadcast domain
- Network Address: The first IP in the range is typically used as the network address
Use Cases
- Small Businesses:
- Perfect for offices with 25-50 devices
- Easy to manage and secure
- Large Enterprises:
- Can create multiple subnets for different departments or locations
- Improved security through subnet segmentation
- Data Centers:
- Critical for organizing server farms
- Allows for precise traffic control between services
Conclusion
Subnetting is essential for any network of reasonable size, as it provides better organization, performance, and security compared to using a single large flat network.