Subnetting
How do we find a destination host, given that we know its IP address on the internet?
Interface: connection between host/router and physical link
Subnet: Device interfaces that can physically reach eachother without passing through an intervening router
IP addresses: 32-bit identifier with a subnet part and a host part
Given: 223.1.1.1:
- the last 3 bits are free for internal IPs
Given: 223.1.1.0/24, humans can interpret this as 24 bits are dedicated to the subnet
- The final 8 bits are for interfaces
Example 1
- Given IP address: 223.1.1.1, subnet mask: 255.255.255.248
- Subnet address? 223.1.1.0/29
Example 2
- IP address: 129.17.129.97/27:
- Network/organization address?
- 129.17.129.96
- Subnet?
- 255.255.255.224
- Total IP addresses?
- 32
- Assignable IP addresses?
- 30
- Range?
- 129.17.129.01111111
- Network/organization address?
- Say the organization wants the network divided into 4 equal size subnets. For each, write:
- Subnet size
- Subnet address (CIDR)
- Subnet mask
- Range of usable IPs
- Broadcast address
- A
- 129.17.129.011 00 000
- 011 is part of the 27 bits
- 00 is A
- 000 is remainder of subnet address
- 01100000 is 96 in binary
- 129.17.129.96/29
- 255.255.255.11111000 -> 255.255.255.248
- 129.17.129.011 00 000