[Ccna]-04-ip address and subnet mask in detail (mainly introduced IPv4)

Introduction

This article describes what the IP address and its function and IP address composition, IP address classification, IP subnet partition, subnet mask, public address, private address,VLSM (variable eldest son netmask), CIDR (Non-class inter-domain routing) and other CCNA basics.

Article Directory

0x1. What is an IP address
the role of the 0X2.IP address
0x3.ipv4 Address Composition
0x4.ipv4 Address Categories
A. Reserved IP address
B. Private IP address
c. Special IP address
0x5.ip Sub-network Division
A. Problems with IP addresses that are not divided into subnets
B. The IP address of the network that is zoned for its benefits
c. Network Segment
D. Masks by default
E. Subnet Mask
F. Calculation of subnetting
G. Subnetting example-C class address
0x6.vlsm (variable eldest son netmask)
0x7.cidr (Non-class inter-domain routing)
A.CIDR Example
B.cidr calculation Method

0x1. What is an IP address

An IP address is an Internet protocol address that is designed to communicate with each other in connection with a computer network. IP protocol provides a unified address format for each network on the Internet and each host is assigned a logical address common IP address, divided into IPv4 and IPv6 two major categories. IPV4 addresses are usually expressed as "dotted decimal" (a.b.c.d), where a,b,c,d are 0~255 decimal integers IPv4 address length 4bytes=32bits

The role of the 0X2.IP address

The address used to represent a single node

0x3.ipv4 Address composition

A IPV4 address consists of two main parts: a part that identifies the network number to which the address belongs, and a part that identifies a particular host in the network.

0x4.ipv4 Address Categories

How to differentiate IP addresses from a, B, C, D, E class: starting with a few bits from the first eight-bit group

Compute the available host addresses:2 of the N minor minus 2

A. Reserved IP address

The number of hosts actually accommodated in each network is the number of theoretical hosts minus 2, because two addresses are reserved:

Network address-The network location is unchanged, the host location of the 0 address, indicating that the network itself, such as the 192.168.1.0/24 broadcast address-the network bit is unchanged, the host bit 1 address, representing the broadcast of this network, such as 192.168.1.255/24 (/24 indicates that the network bit is 24 bits, That is, the subnet mask is 255.255.255.0)

B. Private IP Address

RFC1918 set three private address, as an internal network use, divided into three categories: Class A: 10.0.0.0-10.255.255.255 (a total of 2^24) Class B: 172.16.0.0-172.31.255.255 (Total 2^ 20) Class C: 192.168.0.0-192.168.255.255 (a total of 2^16)

Routes on the Internet do not configure these IP addresses, and if there are packets going to those private addresses, they are discarded by the route.
With these private address segments, some organizations or groups only need a public network IP, through the port address translation (PAT) for internal and external network communication, now the Internet IPv4 address is still not consumed, the private address is not.

C. Special IP Address

IP address 127.0.0.1: Local loopback (loopback) test address. 127.0.0.1 represents the local loopback address, verifying that the local TCP/IP protocol cluster is installed correctly with IP address 255.255.255.255: Broadcast address. IP address 0.0.0.0: Represents any network. The host bit is all 1: Represents the broadcast address of the network segment, that is, all the hosts of the network segment. The host bit is all 0: represents the network address of the network.

0x5.ip subnetting A. IP address of the subnet is not divided by its problems

Problem with non-partitioned IP address: address wasted , broadcast domain too large

B. The IP address of the network that is zoned for its benefits

Benefits of subnetting: 1. Reduce network traffic 2. Optimize network performance 3. Simplified management 4. Greater flexibility in the formation of large coverage networks

C. Network segment

One interface of a router occupies a network segment a segment can only be used by one interface of the router

D. Masks by default

IP address: 172.16.2.160    Mask: 255.255.0.0
By default, subnets are not divided

E. Subnet mask

IP address: 172.16.2.160    Subnet Mask: 255.255.255.0

"/16" means that the subnet mask has a 16-bit "/24" indicating that the subnet mask has 24 bits

IP address: 172.16.2.160    Subnet Mask: 255.255.255.192

Extended 10-bit subnet address

The core idea of subnetting: "borrowing" a host bit to "make" a new "network "

F. Calculation of subnetting

1. How many subnets will be generated by the subnet mask you choose?    2 x-Square (x: Subnet) 2. How many hosts can I have per subnet?    2 Y-side -2 (y: host-digit) 3. Effective subnets (block size)?    Block size =2 y (y: Host bits)    (the result is block size or base number) 4. What is the broadcast address for each subnet?    The host bits are all 1. (Broadcast address = lower Subnet number-1) 5. What are the valid hosts for each subnet?    Ignore all 0 and all 1 addresses in the subnet, and the rest is the valid host address.

G. Subnetting example-C class address

IP address: 192.168.5.139    Subnet Mask: 255.255.255.224

0X6.VLSM (variable eldest son netmask)

The appearance of the variable eldest son netmask (variable-length Subnet masks,vlsm) is to break the traditional class-based address partitioning method, which is to alleviate the shortage of IP address ; function: Save IP address space ; Reduce the routing table size; Note: When using VLSM, the routing protocol used must be able to support it, these routing protocols include RIPV2,OSPF,EIGRP and BGP;

0X7.CIDR (Non-class inter-domain routing)

The concept of CIDR: ignoring the rules of a, B, Class C network, defining a set of networks with the same prefix as a block, or a route entry. (e.g. 199.0.0.0/8) The advantages of CIDR:    reduced network number, reduced routing table, lower    overhead from network traffic, CPU, and memory, and greater flexibility when addressing the    network;

A.CIDR Example

B.cidr calculation method

[Ccna]-04-ip address and subnet mask in detail (mainly introduced IPv4)