find my ip address
Addressing in IP-networks
Address Type: physical (MAC-address), network (IP-address) and symbolic (DNS-name)
Every computer on the network TCP / IP address has three levels:
Local host address defined by the technology, which is a separate network, which includes this site. For nodes that are members of the local network - the MAC address of a network adapter or router port, such as 11-A0-17-3D-BC-01. These addresses are appointed by the manufacturers and are unique addresses as well as managed centrally. For all existing technologies LAN MAC address is 6 bytes format: Senior 3 bytes - identifier of the manufacturer, and the younger 3 bytes assigned a unique way by the manufacturer. For nodes that are members of global networks such as X.25 or frame relay, local address of the administrator appointed by a global network.
IP-address, which consists of 4 bytes, for example, 126.96.36.199. This address is used at the network level. He is appointed by the administrator during the configuration of computers and routers. IP-address consists of two parts: the number of network and node numbers. Network number can be selected at random, or appointed on the recommendation of a special Internet (Network Information Center, NIC), if the network should operate as a component of the Internet. Typically, Internet service providers have a range of addresses in units of NIC, and then distributes them among its subscribers.
Number of nodes in the IP protocol is assigned independently of the local host address. The division of IP-addresses on the field numbers and the number of network nodes - flexible, and the border between these fields may be set quite arbitrarily. The node can enter multiple IP-networks. In this case the node must have multiple IP-addresses, according to the number of network connections. Thus IP-address was not a single computer or router and a network connection.
Character identifier name, for example, SERV1.IBM.COM. This address is assigned administrator, and consists of several parts, such as the hostname, name of organization, the domain name. This address, also known as DNS-name, used at the application level, for example, in the protocols FTP or telnet.
The three main classes of IP-addresses
IP-address has a length of 4 bytes and is usually written as four numbers representing the values of each byte in decimal form, separated by periods, such as:
188.8.131.52 - traditional decimal format for addresses
10000000 00001010 00000010 00011110 - binary format is the same address.
Figure 3.1 shows the structure of IP-addresses.
0 N N node network
1 0 N N node network
1 1 0 N N node network
1 1 1 0 multicast group address
1 1 1 1 0 Reserved
Fig. 3.1. The structure of IP addresses
Address consists of two logical parts - the number of network and node numbers in the network. Which part of the address refers to the network number and which number of nodes is determined by the value of the first bits of the address:
If the address begins with 0, the network is assigned to Class A, and the network number is one byte, the remaining 3 bytes are interpreted as the number of nodes in the network. Class A networks have a number ranging from 1 to 126. (Number 0 is not used, and the number 127 is reserved for special purposes, as described below.) In Class A networks, the number of nodes must be greater than 216, but does not exceed 224.
If the first two bits of the address is 10, the network belongs to the class B and is a network of moderate size with the number of units 28 - 216. In class B networks by a network address and the address of a site devoted to 16 bits, ie, 2 bytes.
If the address begins with a sequence of 110, the network of P with the number of nodes less than 28. A network address has 24 bits, and the address of the node - 8 bits.
If the address begins with a sequence of 1110, he was a class D address, and indicates a special group address - multicast. If the package as a destination address given the address of class D, then the package must have all units covered by a given address.
If the address begins with a sequence of 11110, the address of the class E, it is reserved for future applications.
In the table below shows the range of networks corresponding to each class of networks.
Class Minimum Maximum mail address
A 01.0.0 184.108.40.206
B 220.127.116.11 18.104.22.168
C 22.214.171.124. 126.96.36.199
D 188.8.131.52 184.108.40.206
E 240.0.0.0 247.255.255.255
Agreement on Special addresses: broadcast, multicast, loopback
In the IP protocol, there is some agreement on the interpretation of IP-addresses:
if the IP address consists of binary zeros,
0 0 0 0 ................................... 0 0 0 0
it indicates the address of the node that generated this packet;
if in the network numbers are 0,
0 0 0 0 ....... 0 Number of nodes
then by default it is considered that the site belongs to the same network as the node that sent the packet;
if all bit IP-addresses are 1,
1 1 1 1 ......................................... 1 1
the packet with the destination addresses must be distributed to all nodes located in the same network as the source of the package. This newsletter is called the limited broadcast (limited broadcast);
if the destination address in the box are solid, 1
Number of Network 1111 ................ 11
the packet with that address is sent to all nodes of the network with a given number. This newsletter is called broadcast communication (broadcast);
address 127.0.0.1 is reserved for feedback when testing of the software without a real hub of sending a package over the network. This address is called loopback.
Already mentioned the form of group IP-address - multicast - means that the package must be delivered to several sites, which form a group with the number specified in the address field. Nodes themselves identify themselves, that is, determine to which group they belong. The same node can be included in several groups. Such reports, as opposed to broadcast called multiveschatelnymi. The group address is not divisible by the field number and the network node and processed by a router especially.
In the IP protocol has no concept of broadcast, in the sense in which it is used in link layer protocols, local area networks, where data must be delivered to any and all sites. As the limited broadcast IP-address, and broadcast IP-address are the limits of distribution in InterNetwork - they are limited by either the network to which the node - the source of the package, or network number specified in the destination address. Therefore, the division of the network using routers on a broadcast storm of the isolates from one part of an overall network parts, simply because there is no way to send a package at the same time to all nodes of a network of networks.
Displays the physical address to IP-address: The ARP and RARP
The minutes of IP-address of the node, ie, address or port of the router is assigned a random network administrator and do not directly linked to its local address, such as, for example, the protocol IPX. The approach used in the IP, is convenient to use in large networks, and because of his independence from the format of local address, and because of stability, because otherwise, when changing the network adapter on your computer so the change should have taken into account all recipients worldwide Internet (based in that case, of course, if the network is connected to Internet'u).
Local address is used only in the IP protocol in the network with data exchange between the router and the hub of this network. The router received a package for the site of one of the networks directly connected to its ports, to transfer the package to form a frame in accordance with the requirements of this network technology and state of the local host address, such as its MAC address. In the package came this address is not specified, so the router to the challenge of searching for a known IP-address that is specified in the packet as a destination address. A similar challenge is faced and the final node, when it wants to send a package to the remote network through a router connected to the same network as this node.
To determine the local address on the IP-address used by permission of the protocol addresses of Address Resolution Protocol, ARP. The ARP works in different ways depending on whether the link layer protocol operates in the network - the LAN protocol (Ethernet, Token Ring, FDDI) broadcast, with the possibility of access to all nodes of the network, or global network protocol (X.25, frame relay), as a rule do not support the broadcast access. There is also a protocol, a critical inverse problem - to find IP-address of a known local address. It is called reverse ARP - RARP (Reverse Address Resolution Protocol) and is used at startup diskless stations, not knowing at the initial moment of its IP-address, but knowing the address of its network adapter.
In the LAN protocol uses a broadcast ARP frame link layer protocol to search the network node with the given IP-address.
Site that you need to perform mapping of IP-addresses to a local address, forms the ARP request, puts it in the frame protocol link layer, indicating a well-known in the IP-address, and sends a broadcast request. All network nodes receive ARP request and compare a specified IP-address with its own. In the case of convergence node shapes ARP-reply, which indicates its IP-address and a local address and sends it to have direction as in the ARP request sender specifies a local address. ARP-requests and responses use the same size package. As the local addresses are in different types of networks have different lengths, the ARP protocol packet format depends on the type of network. Figure 3.2 shows the protocol ARP packet format for transmission over a network Ethernet.
0 8 16 31
Type the network protocol type
The length of the local address of the Network Address Length Transaction
Local address (bytes 0 - 3)
Local address of the sender (bytes 4 - 5) IP-address (bytes 0-1)
IP-address (bytes 2-3) Seeking a local address (bytes 0 - 1)
Seeking a local address (bytes 2-5)
Seeking IP-address (bytes 0 - 3)
Fig. 3.2. The ARP packet format
In the type of networks to Ethernet networks indicated a value of 1. Field type protocol allows the use of ARP packets, not only for protocol IP, but also for other network protocols. For the IP value of this field is 080016.
The length of a local address for the Ethernet protocol is 6 bytes, and the length of IP-address - 4 bytes. In the operation for ARP requests indicates a value of 1 for the ARP protocol, and 2 for the protocol RARP.
The node that sends the ARP-request, fills in the packet all the fields except the fields desired local address (to RARP-query does not specify the required IP-address). The value of this field is filled by a node, identified his IP-address.
As global networks network administrator often had to manually build ARP-table, in which he asks, for example, with IP-address at the node network X.25, which is worth a local address. Recently, the trend of automation of the ARP protocol and global networks. For this purpose, among all the routers connected to a global network, is allocated a special router, which is ARP-table for all the remaining nodes and routers of the network. With this centralized approach for all nodes and routers need to manually set the only IP-address and local address of the selected router. Then each node and the router registers its address in the highlighted router and, if necessary, to establish correspondence between the IP-address and local address site appeals to a dedicated router to automatically request and receive a response without the involvement of the administrator.
Display character address in the IP-address: the DNS service
DNS (Domain Name System) - is a distributed database that supports the hierarchical system of names for the identification of sites on the Internet. DNS Service is designed for automatic IP-address on the famous character of the node. DNS specification defines the standards RFC 1034 and 1035. DNS requires static configuration of its tables, displaying the names of the computers in the IP-address.
DNS protocol is an application layer protocol office. This protocol nesimmetrichen - it defines DNS-DNS-servers and clients. DNS-servers keep part of a distributed database on line symbolic names and IP-addresses. This database is distributed administrative domains the Internet. Clients of the DNS server know the IP-address of the DNS server of its administrative domain and IP transfer protocol request, which indicate the well-known character's name and asked to return the corresponding IP-address.
If the data requested under stored in the database of the DNS-server, it immediately sends the client response, if not - then it sends a query DNS-server of another domain that can handle the request himself or refer it to another DNS-server. All DNS-servers are connected hierarchically, in accordance with the hierarchy of domains the Internet. Customer queries these name servers until it finds the correct mapping. This process is accelerated because of fact that name servers cache information continuously provided on request. Client computers can be used by IP-addresses several DNS-servers, to improve the reliability of their work.
DNS database has a tree structure, called the domain namespace, in which each domain (tree node) is addressed and may contain subdomains. A domain name identifies its position in the database in relation to the parent domain, and the points are separated in the name of the corresponding nodes of the domain.
The root DNS database is managed by Center for Internet Network Information Center. Top-level domains are assigned to each country, as well as the organizational basis. The names of these domains should follow the international standard ISO 3166. For designations of the two-and three used abbreviations, and for different types of organizations use the following abbreviations:
com - Commercial organizations (eg, microsoft.com);
edu - educational (eg, mit.edu);
gov - government agencies (eg, nsf.gov);
org - nonprofit organizations (eg, fidonet.org);
net - the organization that support networks (eg, nsf.net).
Each DNS domain is administered by a separate organization, which usually splits its domain in subdomains, and passes the function of administration of these subdomains to other organizations. Each domain has a unique name and each sub has a unique name within its domain. A domain name can contain up to 63 characters. Each host on the Internet is uniquely determined by its fully qualified domain name (fully qualified domain name, FQDN), which includes the names of all domains in the direction of the host root. Example of full DNS-name:
Automating the process of destination IP-addresses of network nodes - Protocol DHCP
As mentioned above, IP-address may be appointed administrator of the network manually. This is the administrator for the tiresome procedure. The situation is further complicated by the fact that many users do not have sufficient knowledge to configure their computers to work in InterNetwork, and must therefore rely on the administrators.
Protocol Dynamic Host Configuration Protocol (DHCP) was designed to relieve the administrator of these problems. The basic purpose of DHCP is a dynamic IP-addresses. However, except for Dynamic, DHCP can support and more simple ways of manual and automatic static assignment of addresses.
In the manual procedure for the appointment addresses the active involvement of the administrator, which provides a DHCP-server information on the relevant IP-addresses to physical addresses or other identifiers of clients. These addresses are reported to clients in response to their requests to the DHCP-server.
In automatic mode the static DHCP-server assigns the IP-address (and possibly other configuration parameters the client) from the pool of available IP-addresses, without operator intervention. The boundaries of the pool designated by the administrator sets the addresses in the DHCP-server configuration. Between the client ID and its IP-address is still, as with the manual assignment, there is a permanent line. It was established at the time of initial appointment server DHCP IP-address of the client. For all subsequent requests the server returns the same IP-address.
When dynamic allocation of addresses DHCP-server gives the client the address for a limited time, allowing later re-use IP-addresses of other computers. Dynamic separation of addresses allows to build IP-network, the number of nodes in which far exceeds the number available to the administrator of IP-addresses.
DHCP provides safe and easy way to configure the network TCP / IP, ensuring no conflicts addresses through centralized management of their distribution. The Administrator manages the process of destination addresses by using the "duration of the lease" (lease duration), which determines how long the computer can use the assigned IP-address, before again requesting it from a DHCP server lease.