IP Addressing

IP Addressing(处理)

• Each host on Internet has unique 32 bit IP address
• Each address has two parts: netid and hostid
• netid(网络号) is unique & administered(管理） by Internet registration(注册)
• netid facilitates(促进) routing and reduces routing table
• A separate address is required for each physical connection of a host to a network; “multi-homed” hosts
• Dotted-Decimal Notation:
  int1.int2.int3.int4 where intj = integer value of jth octet
• IP address of 10000000 10000111 01000100 00000101
  is 128.135.68.5 in dotted-decimal notation

Reflections

• How to reduces routing table: The netid sorts IP Addresses, combing the IP Addresses which belong to the same places to the same netid.

Classful Addresses

1. Up to 250 million multicast groups at the same time
2. Permanent group addresses

• All systems in LAN; All routers in LAN;
• All OSPF routers on LAN; All designated OSPF routers on a LAN, etc.

1. Temporary groups addresses created as needed
2. Special multicast routers

Reserved Host IDs (all 0s & 1s)

• Internet address used to refer to network has hostid set to all 0s
  

• Broadcast address has hostid set to all 1s
  

Private IP Addresses

• Specific ranges of IP addresses set aside for use in private networks (RFC 1918)
• Use restricted to private internets; routers in public Internet discard packets with these addresses
• Range 1: 10.0.0.0 to 10.255.255.255
• Range 2: 172.16.0.0 to 172.31.255.255
• Range 3: 192.168.0.0 to 192.168.255.255
• Network Address Translation (NAT)** used to convert** between private & global IP addresses

Example of IP Addressing

Subnets

• Subnets allow a network to be split into several parts for internal use, but the network still act like a single network to the outside.