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Lesson 5Design a functional TCP/IP solution
Objective Define the elements utilized in TCP/IP design.

Design a functional TCP/IP Solution

To determine the appropriate TCP/IP infrastructure, you must evaluate your Internet accessibility needs, the use of routers, and public IP address availability. To allow peer-to-peer communication, all hosts in a TCP/IP network require unique IP addresses. IP 4.0 supports a 32-bit address structure, publicly administered by a standards body (IETF), which can be used to implement both public and private address structures.
The following four factors must be taken into consideration when designing a functional IP network:
  1. The IP address and mask configuration
  2. The addressing structures for private network operation
  3. The addressing structures to allow subnet routing
  4. A methodology for a consistent design of IP networks

This lesson will review IP addressing. Future lessons will look at other essential aspects of designing with TCP/IP.

IP addressing

Each TCP/IP host is identified by a logical IP address. This address is unique for each host that communicates by using TCP/IP. Because IP addresseses identify devices on a network, you must assign a unique IP address to each device on the network. The standard for IP addressing is referred to as IP version 4.0 (v4). The standard uses a 32-bit address field and 32-bit subnet mask field. The following Slide Show covers the essentials of IP addressing.

  1. Depending on the routing protocols used, you can specify IP addresses based on: 1) Network Classes (A,B,C) with an associated classful default subnet mask. 2) Classes with variable length, subnet masks (VLSM) , 3) (CIDR) Classless Inter-Domain Routing with a specified prefix length
  2. The Class B default subnet mask is 255.255.0.0. Another way to characterize the default Class B subnet mask is to use the classless notation or 'slash' notation.
  3. Class-based networks support a single subnet mask, and are suitable for networks routed by using Routing Information Protocol (RIP) 1.0 VLSM and CIDR support multiple masks or prefixes per network.
  4. Class based IP addresses are split into two portions, 1) network ID and 2) host ID. The subnet mask is used to define which portion of the IP address defines the network ID.

ip Addressing Review
When using class-based addresses and VLSM, you cannot decrease the number of bits that determine the network ID below the number that is assigned to the default subnet mask.
The following table lists and describes the RFCs pertaining to subnet masks.

RFC Reference title Describes
950 Internet Standard Subnetting Procedure Subnetting of IP addresses
1518 An Architecture IP Address Allocation with CIDR Introduction to the architecture required to support CIDR
1519 Classless Inter-Domain Routing (CIDR) an Address Assignment and Aggregation Strategy Designing with route aggregation
1812 Requirements for IPv4 Routers, Section 4.2.2.11 All ones and zeros in the IP address mask
1878 Variable Length Subnet Table For IPv4 Subnet masking of variable length
The next lesson explores IP addressing for a private network.