10 Aug 2023
IPv4
ipv4
- 32 bit addresses divided into 8 bit blocks.
- Has private address range and multicast address range.
Classful networking
- 0xxxxxxx.x.x.x is one network. Called class A.
- Has 128 possible networks. Size of network is 224
- Has subnet mask equal to 8.
- Similarly 10xxxxxx.x.x.x is another network. Class B.
- Has 214 networks. Network size decreases inversely.
- Has subnet mask equal to 16.
- Similarly class C has subnet of 24.
- Only allowed for 254 networks.
Fun fact: ARPAnet was 10.x.x.x
private address range
| Block Size | Range | Bit mask | Classful description |
|---|---|---|---|
| 24-bit | 10.0.0.0 - 10.255.255.255 | 8 | One class A network |
| 20 bit | 172.16.0.0 - 172.31.255.255 | 12 | 16 contiguous class B networks |
| 12 bit | 192.168.0.0 - 192.168.255.255 | 16 | 256 contiguous class C networks |
Loopback interface
- Special case of private addresses.
- Packets never leave the host.
- 127.0.0.0/8 is the address space reserved for ipv4.
IP Broadcast
- In IPv4 it has a special address. This was used by interfaces to send messages to all networks connected to a particular subnet.
- In dhcp, if the broadcast address of the subnet is not defined, then a DHCPDISCOVER message is sent to the address 255.255.255.255.
- This again does the same job of keeping the broadcast message within the same subnet.
- The broadcast address is otherwise calculated as follows: - Take the first subnet bits of the network. Let them be as they are. - Change the remaining trailing bits to 1.
