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CompTIA A+ Certification All-in-One Exam Guide

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NOTE The unspecified address (all zeros) can never be used, and neither

can an address that contains all ones (in binary) or all fs (in hex notation).

IPv6 uses the “/x” prefix length naming convention, similar to the CIDR

naming convention in IPv4. Here’s how to write an IP address and prefix

length for a typical IPv6 host:

fe80::cf:0:ba98:1234/64

SIM Check out the excellent “IPv6 Address” Type! simulation in the

Chapter 19 section of http://totalsem.com/100x. It’s good for reinforcing your

knowledge of IPv6 and getting practice with performance-based questions.

Where Do IPv6 Addresses Come From?

With IPv4, IP addresses come from one of two places: either you type in the

IP address yourself (static IP addressing) or you use DHCP (also called

dynamic IP addressing). With IPv6, addressing works very differently.

Instead of one IP address, you will have multiple IPv6 addresses on a single

network card.

When a computer running IPv6 first boots up, it gives itself a link-local

address, IPv6’s equivalent to IPv4’s APIPA/zeroconf address. Although an

APIPA/zeroconf address can indicate a loss of network connectivity or a

problem with the DHCP server, computers running IPv6 always have a linklocal

address. The first 64 bits of a link-local address are always fe80::. That

means every address always begins with fe80:0000:0000:0000. If your

operating system supports IPv6 and IPv6 is enabled, you can see this address.

Figure 19-14 shows the link-local address for a typical system running the

ipconfig utility.

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