This topic describes how IPv6 addresses are shown in hexadecimal and the appropriate methods for abbreviation of addresses.
IPv6 Address Representation
• x:x:x:x:x:x:x:x, where x is a 16-bit hexadecimal field
- Case-insensitive for hexadecimal A, B, C, D, E, and F
• Leading zeros in a field are optional:
• Successive fields of 0 can be represented as ::, but only once per address.
Colons separate entries in a series of 16-bit hexadecimal fields that represent IPv6 addresses. The hexadecimal digits A, B, C, D, E, and F represented in IPv6 are case-insensitive.
IPv6 does not require explicit address string notation. Use the following guidelines for IPv6 address string notations:
■ The leading zeros in a field are optional, so that 09C0 = 9C0 and 0000 = 0.
■ Successive fields of zeros can be represented as "::" only once in an address.
■ An unspecified address is written as "::" because it contains only zeros.
Using the "::" notation greatly reduces the size of most addresses. For example, FF01:0:0:0:0:0:0:1 becomes FF01::1.
Note An address parser identifies the number of missing zeros by separating the two parts and entering 0 until the 128 bits are complete. If two "::" notations are placed in the address, there is no way to identify the size of each block of zeros.
8-16 Building Scalable Cisco Internetworks (BSCI) v3.0 © 2006 Cisco Systems, Inc.
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