Copyright Goodheart-Willcox Co., Inc. 258 Principles of Cybersecurity Address Meaning The length of the address is increased from 32 bits in IPv4 to 128 bits. IPv6 also has eight sections of hexadecimal quartets. Quartets are often called hextets. Each quartet, or hextet, represents 16 binary bits. The sections are separated by a colon (:) in IPv6 as opposed to a period (.) separating the octets in IPv4. An IPv6 address looks something like this: 2001:203A:0000:0000:5300:0000:0027:8A9C At fi rst glance, it might seem an address in this format would be hard to remember. However, there are some key things to know about an IPv6 address: • Portions of the address indicate the network address and the host address. • The fi rst quartet in the address identifi es the type of IPv6 address, such as public or private. • The address possibly can be shortened. An IPv6 address is shortened by removing consecutive sections of zeros. These sections can be shortened to two colons (::), but only once in an address hextet or quartet. A single section of 0000 can be shortened to a single 0. Leading zeros in a quartet can be removed. Using the above example, the address can be shortened: 2001:203A:0000:0000:5300:0000:0027:8A9C (unshortened address) 2001:203A::5300:0:27:8A9C (same address in shortened form) Notice the two consecutive sections of zeros have been removed (::), and the single section of zeros has been reduced to a single zero. Hexadecimal Conversion With the help of conversion calculators and basic math principles, you can convert data from hexadecimal, or hex, to decimal. Look at Figure 8-8. This shows the properties of a packet as reported by the packet sniffer Wireshark, which is discussed later in this chapter. The Time to live: value of 64 is represented as 40 in hexadecimal. Consider a hexadecimal value of 40 and refer to Figure 8-9. Each digit in the hexadecimal value is a placeholder. The 0 is equivalent to 160. The 4 is equivalent to 161. Taking 16 to the power of 0 is the decimal value of 1. Taking 16 to the power of 1 is the decimal value of 16. To compute the value, multiply each value by the placeholder and add them together. (0 × 1) + (4 × 16) = 64. The decimal equivalent of the hexadecimal value 40 is 64. IPv6 Host vs. Network In the IPv6 protocol, the fi rst 64 bits of an address identify the network, as shown in Figure 8-10. The last 64 bits identify the host. The fi rst 48 bits represent Hexidecimal conversion is covered in detail in Chapter 17. FYI Goodheart-Willcox Publisher Figure 8-7. The hexadecimal numbering system has values of 0–9 and A–F. Numbering System Number Decimal 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Hexadecimal 0 1 2 3 4 5 6 7 8 9 A B C D E F Examples Decimal Hexadecimal 77 4D 101 65 1966 7AE