Networking Notes 2 - Addressing

Network Notes 2

IPv4

Each IPv4 have 4 byte, 5 classes

Class - 2-level hierarchy of IP address(Netid+Hostid)

• A: Byte1 Netid; Byte2,3,4 Hostid
• B: Byte1,2 Netid; Byte 3,4 Hostid
• C: Byte1,2,3 Netid; Byte 4 Hostid
• D: The address range of IP Multicast, is 224.0.0.0 ~ 239.255.255.255.
• E: The address range of ?,240.0.0.0~255.255.255.255

I should only focus on ABC here.

The 2-level hierarchy of IP addresses is not sufficient for organizations

Subnetting

We usually want to division of a network into smaller networks(subnet).

We have 3 level of IDs of hierarchy

• NetID
• SubnetID
• HostID

In a subnet, Device can phtsically reach each other without intervening router.

Masking

Masking is the process of extracting the network address from an IP address

• Default Mask: used by routers outside
• Subnet MaskL used by route inside

Mask

• 32 bits long
• NetID = 1
• HostID = 0

IP address Essentially a binary number
Example:
11111111 00000000 00000000 00000000 = 255.0.0.0

Masking is AND operation of the IP address

The 11111111 is the netID and the 0s is HostID.

NetIDs are managed by Regional Internet Registries

• APNIC (Asia)
• ARIN (American)
• LACNIC (Latin American)
• RIPE NCC (Europe)
  HostIDs are managed by the network administrator(owner of the NetID)

CIDR - Classless InterDomain Routing

The length of the network prefix in IP addresses is kept arbitrary.