640-802 CCNA Study Guide - Elktech.org

Cisco 640-802 Exam
The key to a successful IPv6 transition is compatibility with the large installed base of IPv4 hosts
and routers. Maintaining compatibility with IPv4 while deploying IPv6 will streamline the task of
transitioning the Internet to IPv6. This specification defines a set of mechanisms that IPv6 hosts
and routers may implement in order to be compatible with IPv4 hosts and routers.
The mechanisms in this document are designed to be employed by IPv6 hosts and routers that
need to interoperate with IPv4 hosts and utilize IPv4 routing infrastructures. We eXPect that most
nodes in the Internet will need such compatibility for a long time to come, and perhaps even
indefinitely. However, IPv6 may be used in some environments where interoperability with IPv4 is
not required. IPv6 nodes that are designed to be used in such environments need not use or even
implement these mechanisms. The mechanisms specified here includE.
- Dual IP layer (also known as Dual Stack): A technique for providing complete support for both
Internet protocols -- IPv4 and IPv6 -- in hosts and routers.
- Configured tunneling of IPv6 over IPv4: Point-to-point tunnels made by encapsulating IPv6
packets within IPv4 headers to carry them over IPv4 routing infrastructures.
- IPv4-compatible IPv6 addresses: An IPv6 address format that employs embedded IPv4
addresses.
QUESTION NO: 250
Identify the four valid IPv6 addresses. (Choose four.)
A. ::
B. ::192:168:0:1
C. 2000::
D. 2001:3452:4952:2837::
E. 2002:c0a8:101::42
F. 2003: deaD. beef:4dad:23:46:bB. 101
Answer: A,B,E,F
Explanation:
IPv6 addresses are normally written as eight groups of four hexadecimal digits, where each group
is separated by a colon (:). For example, 2001:0db8:85a3:0000:0000:8a2e:0370:7334 is a valid
IPv6 address. To shorten the writing and presentation of addresses, several simplifications to the
notation are permitted.
Any leading zeros in a group may be omitted; thus, the given example becomes
2001:db8:85a3:0:0:8a2e:370:7334 One or any number of consecutive groups of 0 value may be
replaced with two colons (::): 2001:db8:85a3::8a2e:370:7334
This substitution with double-colon may be performed only once in an address, because multiple
occurrences would lead to ambiguity. For example, the illegal address notation 2001::FFD3::57ab,
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