1 Subnetting ITEC 370 George Vaughan Franklin University

2 Sources for Slides Material in these slides comes primarily from course text, Guide to Networking Essentials,Tomsho, Tittel, Johnson (2007). Other sources are cited in line and listed in reference section.

3 TCP/IP and OSI Models

4 Some Simple Binary Arithmetic Tomsho, Tittel, Johnson (2007) Four kinds of binary calculations: –Converting between binary and decimal –Converting between decimal and binary –Understanding how setting high-order bits to the value of 1 in 8-bit binary numbers corresponds to specific decimal numbers –Recognizing the decimal values for numbers that correspond to low-order bits when set to 1

5 Converting Decimal to Binary Tomsho, Tittel, Johnson (2007) 125 is converted to binary as follows: –125 divided by 2 equals 62, remainder 1 –62 divided by 2 equals 31, remainder 0 –31 divided by 2 equals 15, remainder 1 –15 divided by 2 equals 7, remainder 1 –7 divided by 2 equals 3, remainder 1 –3 divided by 2 equals 1, remainder 1 –1 divided by 2 equals 0, remainder 1

6 Converting Binary to Decimal Tomsho, Tittel, Johnson (2007) To convert to decimal: 1.Count the total number of digits in the number (8) 2.Subtract one from the total (8 - 1 = 7) 3.That number (7) is the power of 2 to associate with the highest exponent for two in the number 4.Convert to exponential notation, using all the digits as multipliers , therefore, converts to:

7 High-Order Bit Patterns Tomsho, Tittel, Johnson (2007)

8 Low-Order Bit Patterns Tomsho, Tittel, Johnson (2007)

9 Types of IP Addressing The demarcation point in the 32 bit address between network ID and host ID depends on addressing scheme: –Class Based Addressing generally uses a byte boundary as the dividing point –Classless Based Addressing uses a bit boundary.

10 Class Based IP Addressing (Cisco – IP Addressing, n.d.). Used less frequently now, CIDR preferred

11 Special IP Addresses Information on this slide from "Private Use" IP addresses: – – – "Autoconfiguration" IP Addresses: – –used automatically by some PCs and Macs when They are configured to use IP Do not have a static IP Address assigned And are unable to obtain an IP address using DHCP. "Loopback" IP addresses: – –Each computer on the Internet uses /8 to identify itself, to itself. – to is earmarked for what is called "loopback". –This construct allows a computer to establish/validate its IP stack. –Most software only uses for loopback purposes

12 Classless Interdomain Routing (CIDR) Division between Network and Host ID is at bit level. Example: /27 –IP address is: –‘/27’ indicates that: First 27 bits define Network ID Last 5 bits define Host ID (defines size of subnet) Subnet Mask = –(binary) –(decimal) Subnet Mask defines Host ID size –1’s used to define which bits belong to Network ID –0’s used to define which bits belong to Host ID Subnet Mask is assigned to host at same time that IP address is assigned.

13 CIDR (Cont.) Mapping class based IP addressing to CIDR: –Class A submask = –Class B submask = –Class C submask = All hosts in same network must use same subnet mask.

14 Subnetting with Classless IP Addressing: Example 1

15 Subnetting with Classless IP Addressing: Example 1 (Continued)

16 Network Diagram of Subnets Subnet Subnet Subnet Subnet Subnet Subnet Subnet Subnet

17 Subnetting with Classless IP Addressing: Example 2

18 Subnetting with Classless IP Addressing: Example 2 (Continued)

19 References Tomsho, Tittel, Johnson (2007). Guide to Networking Essentials. Boston: Thompson Course Technology. Odom, Knott (2006). Networking Basics: CCNA 1 Companion Guide. Indianapolis: Cisco Press Wikipedia (n.d.). OSI Model. Retrieved 09/12/2006 from Cisco – IP Addressing (n.d.). IP Addressing. Retrieved 09/27/2006 from IANA (n.d.) Abuse Issues and IP Addresses. Retrieved 11/11/06 from