22.Cidr. Create supersets. The use of variable length subnet masks.

Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and routing Internet Protocol packets. The Internet Engineering Task Force introduced CIDR in 1993 to replace the previous addressing architecture of classful network design in the Internet. Their goal was to slow the growth of routing tables on routers across the Internet, and to help slow the rapidexhaustion of IPv4 addresses. IP addresses are described as consisting of two groups of bits in the address: the most significant part is the network address, which identifies a whole network or subnet, and the least significant portion is the host identifier, which specifies a particular interface of a host on that network. This division is used as the basis of traffic routing between IP networks and for address allocation policies. Classful network design for IPv4 sized the network address as one or more 8-bit groups, resulting in the blocks of Class A, B, or C addresses. Classless Inter-Domain Routing allocates address space to Internet service providers and end users on any address bit boundary, instead of on 8-bit segments. In IPv6, however, the interface identifier has a fixed size of 64 bits by convention, and smaller subnets are never allocated to end users.CIDR notation is a syntax of specifying IP addresses and their associated routing prefix.

Classless Inter-Domain Routing is based on variable-length subnet masking (VLSM), which allows a network to be divided into variously sized subnets, providing the opportunity to size a network more appropriately for local needs.

VLSM or variable length subnet masking is the more realistic way of subnetting a network to make for the most efficient use of all of the bits.

23.IP routing. Static routing. Dynamic routing.

IP routing is the process of transporting data from source to destination on a determined path across two or more networks. IP routing enables two or more devices on different TCP/IP networks to connect with each other. IP routing provides the path for reaching the destination device.

Static routing is a concept describing one way of configuring path selection of routers in computer networks. It is the type of routing characterized by the absence of communication between routers regarding the current topology of the network. This is achieved by manually adding routes to the routing table. The opposite of static routing is dynamic routing, sometimes also referred to as adaptive routing. In these systems, routes through a data network are described by fixed paths (statically). These routes are usually entered into the router by the system administrator. An entire network can be configured using static routes, but this type of configuration is not fault tolerant.

Adaptive routing describes the capability of a system, through which routes are characterized by their destination, to alter the path that the route takes through the system in response to a change in conditions. The adaptation is intended to allow as many routes as possible to remain valid in response to the change.The term is commonly used in data networking to describe the capability of a network to 'route around' damage, such as loss of a node or a connection between nodes, so long as other path choices are available. There are several protocols used to achieve this:RIP, OSPF, IGRP/EIGRP

Static routing: 1)Manually set up a route in a dormant manner. 2)Stable. 3)Has no impact made by traffic and transmission failures. 3)Creates no traffic derived from routing protocols.

Dynamic routing:1)Automatically sets up a route. 2)Can respond to the changes of the network. 3)Can automatically select the optimized route.

4)Can automatically select the backup route.