Wednesday 22 August 2012

How to Pass Cisco CCNA - Books and Other Study Aids


The CCNA Exam

There are two ways to earn the CCNA certification - pass two individual exams or pass one larger, combined (composite) exam. The exam options are (click the respective links to be taken to the applicable Cisco web page):

Composite exam:

640-802 CCNA - 90 minutes, 45-55 questions
Or, individual exams:

640-822 ICND1 - 90 minutes, 40-50 questions
640-816 ICND2 - 75-90 minutes, 40-50 questions
If you are studying by yourself, it is advisable to take the two exams. It IS more expensive but if you try to do it all at once, you will probably spend more money failing and doing repeats in any case!


Cisco CCNA Discovery Course

Studying questions and answers and practicing Router Simulations such as I refer to in this Blog are a very useful way of preparing for the CCNA exam but hey are NOT a substitute for ordinary study. In my College we used the Cisco CCNA Discovery on line course over a period of 2 years (4 semesters - one for each part of the course).  This course is probably too expensive for an individual student but there are good books and other study aids available.

The following is an extract from Cisco's description of the course:

The following demos provide self-guided tours of chapters from each course. After launching a demo, you can navigate through the chapter topics using the index or the arrows, and explore the media-rich, interactive activities and labs to view the types of content available in each curriculum. Please Note: The chapter demos include embedded network simulation and visualization activities that use Packet Tracer, Cisco’s powerful network simulation software. Packet Tracer software is available only to Academy instructors and students free of charge, and must be previously installed on your computer.


(One English company is offering the online course for £297 sterling plus VAT for 12 months use or £447 for 24 months )
http://www.october-systems.co.uk/qc-cisco-ccna-training-course.html   )


Official Exam Certification Guides by Wendell Odom, Cisco Press


The following books are recommended  by Cisco for complete understanding of all CCNA objectives:
1. CCENT/CCNA ICND1 Official Exam Certification Guide by Wendell Odom, Cisco Press. 
2. CCNA ICND2 Official Exam Certification Guide by Wendell Odom, Cisco Press.
The above links are to the Premium Edition, eBook and Practice Test versions of each book. This is also the Third Edition (2011).

Part of the Product Description for the ICND2 book reads:

The exciting new CCNA ICND2 640-816 Official Cert Guide, Premium Edition eBook and Practice Test is a digital-only certification preparation product combining an eBook with enhanced Pearson IT Certification Practice Test. The Premium Edition eBook and Practice Test contains the following items:
  • The CCNA ICND2 Premium Edition Practice Test, including four complete ICND2 practice exams, four full CCNA practice exams, and enhanced practice test features
  • PDF and EPUB formats of the CCNA ICND2 640-816 Official Cert Guide, Third Edition from Cisco Press, which are accessible via your PC, tablet, and Smartphone

I quoted extracts from the Wendell Odom's ICND2 book (Second Edition 2008) in my previous post regarding IPv6 Questions and Answers.

TO BE CONTINUED

Wednesday 15 August 2012

IPv6 Questions and Answers for CCNA Exam 640-802

I have included IPv6 questions and answers from a number of sources including (A) the official Cisco CCNA exam guide book by Wendell Odom, (B) the website www.9tut.com,  (C) Chris Bryant,  (D) Anthony Sequeira and (E) the book "CCNA  Practice Questions" published by Pearson Certification . The Cisco book by Wendell Odom may possibly go more deeply into IPv6 than you  actually need for the CCNA exam so don't be discouraged!


(A) IPv6 Questions and Answers for CCNA Exam from book by Wendell Odom

The following 9 Questions and Answers are from the book "CCNA ICND2 - Official Exam Certification Guide" Cisco Press,  Second Edition (2008) by Wendell Odom

Question A- 1.       Which of the following is the most likely organization from which an enterprise could obtain an administrative assignment of a block of IPv6 global unicast IP addresses?
a.       An ISP
b.       ICANN
c.       An RIR                             
d.       Global unicast addresses are not administratively assigned by an outside organisation.

Answer:  A. One method for IPv6 global unicast address assignment is that ICANN (Internet Corporation for Assigned Network Numbers) allocates large address blocks to RIRs (Regional Internet Registry), RIRs assign smaller address blocks to ISPs (Internet Service Provider), and ISPs assign even smaller address blocks to their customers. 


Question A- 2.       Which of the following is the shortest valid abbreviation for FE80:0000:0000:0100:0000:0000:0000:0123?
a.       FE80::100::123
b.       FE8::1::123
c.       FE80::100:0:0:0:123:4567
d.       FE80:0:0:100::123 

Answer D. Inside a quartet, any leading 0s can be omitted, and one sequence of 1 or more quartets of all 0s can be replaced with double colons (::). The correct answer replaces the longer 3-quartet sequence of 0s with ::. 


Question A- 3 .       Which of the following answers lists a multicast IPv6 address?
a.       2000::1:1234:5678:9ABC
b.       FD80::1:1234:5678:9ABC
c.       FE80::1:1234:5678:9ABC
d.       FF80::1:1234:5678:9ABC

Answer D.
Global unicast addresses begin with 2000::/3, meaning that the first 3 bits match the value in hex 2000.
Similarly, unique local addresses match FD00::/8, and link local addresses match FE80::/10 (values that begin with FE8, FE9, FEA, and FED hex).
Multicast IPv6 addresses begin with FF00::/8, meaning that the first 2 hex digits are F


Question A- 4.       Which of the following answers list either a protocol or function that can be used by a host to dynamically learn its own IPv6 address?
a.       Stateful DHCP
b.       Stateless DHCP
c.       Stateless autoconfiguration
d.       Neighbor Discovery Protocol 

Answer: A and C. IPv6 supports stateful DHCP, which works similarly to IPv4’s DHCP protocol to dynamically assign the entire IP address. Stateless autoconfiguration also allows the assignment by finding the prefix from some nearby router and calculating the interface ID using the EUI-64 format. 

Question A- 5.       Which of the following help allow an IPv6 host to learn the IP address of a default gateway on its subnet?
a.       Stateful DHCP
b.       Stateless RS
c.       Stateless autoconfiguration
d.       Neighbor Discovery Protocol

Answer A and D. Stateless autoconfiguration only helps a host learn and form its own IP address, but it does not help the host learn a default gateway. Stateless RS is not a valid term or feature. Neighbor Discovery Protocol (NDP) is used for several purposes, including the same purpose as ARP in IPv4, and for learning configuration parameters like a default gateway IP address


Question A- 6.       Which of the following are routing protocols that support IPv6?
a.       RIPng
b.       RIP-2
c.       OSPFv2
d.       OSPFv3
e.       OSPFv4

Answer A and D.  OSPFv3, RIPng, EIGRP for IPv6, and MP-BGP4 all support IPv6. (Memory Hint: RIPng could also be regarded as RIP version 3!)

Question A- 7.       In the following configuration, this router’s Fa0/0 interface has a MAC address of 4444.4444.4444. Which of the following IPv6 addresses will the interface use?
ipv6 unicast-routing
ipv6 router rip tag1
interface FastEthernet0/0
ipv6 address 3456::1/64

a.       3456::C444:44FF:FE44:4444
b.       3456::4444:44FF:FE44:4444
c.       3456::1
d.       FE80::1
e.       FE80::6444:44FF:FE44:4444
f.        FE80::4444:4444:4444

Answer C and E. The configuration explicitly assigns the 3456::1 IP address. The interface also forms the EUI-64 interface ID 

(6444:44FF:FE44:4444), adding it to FE80::/64, to form the link local IP address. 

Question A- 8.       In the configuration text in the previous question, RIP was not working on interface Fa0/0. Which of the following configuration commands would enable RIP on Fa0/0?
a.       network 3456::/64
b.       network 3456::/16             
c.       network 3456::1/128
d.       ipv6 rip enable
e.       ipv6 rip tag1 enable

Answer E. RIPng configuration does not use a network command. Instead, the ipv6 rip command is configured on the interface, listing the same tag as on the ipv6 router rip command, and the enable keyword. 

Question A- 9.       Which of the following IPv4-to-IPv6 transition methods allows an IPv4-only host to communicate with an IPv6-only host?
a.       Dual-stack
b.       6to4 tunneling
c.       ISATAP tunneling
d.       NAT-PT

Answer D. Network Address Translation–Protocol Translation (NAT-PT) translates between IPv4 and IPv6, and vice versa. The two tunneling methods allow IPv6 hosts to communicate with other IPv6 hosts, sending the packets through an IPv4 network. Dual-stack allows a host or router to concurrently support both protocols.
[MY NOTE: NAT-PT is the only way an IPv4-only host can communicate with an IPv6-only host.  The other translation methods need  the two protocols to work together with each other.]


(B) IPv6 Questions in www.9tut.com website

The www.9tut.com website has a large number of CCNA exam questions (and Simulations, Simlets, Testlets etc) including  8 questions on IPv6. See
http://www.9tut.com/ccna-ipv6
The following are some of these questions:

Question B- 4. Which two of these statements are true of IPv6 address representation? (Choose two)

A – The first 64 bits represent the dynamically created interface ID.
B – A single interface may be assigned multiple IPV6 addresses of any type.
C – Every IPV6 interface contains at least one loopback address.
D – Leading zeros in an IPV6 16 bit hexadecimal field are mandatory.
Answer: B C   Leading zeros in IPv6 are optional so that 05C7 equals 5C7 and 0000 equals 0. Therefore D is not correct.


Question B- 5. Which three of the following are IPv6 transition mechanisms? (Choose three)
A – 6to4 tunneling
B – GRE tunneling
C – ISATAP tunneling
D – Teredo tunneling
E – VPN tunneling
F – PPP tunneling
Answer: A C D
Below is a summary of IPv6 transition technologies:
6 to 4 tunneling: This mechanism allows IPv6 sites to communicate with each other over the IPv4 network without explicit tunnel setup. The main advantage of this technology is that it requires no end-node reconfiguration and minimal router configuration but it is not intended as a permanent solution.
ISATAP tunneling (Intra-Site Automatic Tunnel Addressing Protocol): is a mechanism for transmitting IPv6 packets over IPv4 network. The word “automatic” means that once an ISATAP server/router has been set up, only the clients must be configured to connect to it.
Teredo tunneling: This mechanism tunnels IPv6 datagrams within IPv4 UDP datagrams, allowing private IPv4 address and IPv4 NAT traversal to be used.
In fact, GRE tunneling is also a IPv6 transition mechanism but is not mentioned in CCNA so we shouldn’t choose it (there are 4 types of IPv6 transition mechanisms mentioned in CCNA; they are: manual, 6-to-4, Teredo and ISATAP).
[MY NOTE: For the CCNA exam, be sure that you can recognize the NAMES of the 3 main tunneling types i.e. 6 to 4, ISATAP and Teredo ]
Question B- 6. Which two descriptions are correct about characteristics of IPv6 unicast addressing? (Choose two)
A – Global addresses start with 2000::/3.
B – Link-local addresses start with FF00::/10.
C – Link-local addresses start with FE00:/12.
D – There is only one loopback address and it is ::1.
Answer: A D
Below is the list of common kinds of IPv6 addresses:
Loopback address::1
Link-local addressFE80::/10
Unique-local addressFD00::/8 
Global address2000::/3
Multicast addressFF00::/8
[My Note: The 9tut.com answer actually has the Site-local address  prefix FEC0::/10 in place of the Unique-local address prefix FD00::/8 above. However Site-local addresses are now obsolete and have been replaced by Unique-local. ]

Question B- 7. Select the valid IPv6 addresses. (Choose all apply)
A – ::192:168:0:1
B – 2002:c0a8:101::42
C – 2003:dead:beef:4dad:23:46:bb:101
D – ::
E – 2000::
F – 2001:3452:4952:2837::
Answer: A B C D F
Answers A and B  are correct because A is the short form of 0:0:0:0:192:168:0:1 and  B is the short form of 2002:c0a8:0101:0:0:0:0:0042.

Answer C is correct because it is the normal IPv6 address.
Answer D is correct because “::” is named the “unspecified” address and is typically used in the source field of a datagram that is sent by a device that seeks to have its IP address configured.
Answer E is not correct because a global-unicast IPv6 address is started with binary 001, denoted as 2000::/3 in IPv6 and it also known as an aggregatable global unicast address.The 2000:: (in particular, 2000::/3) is just a prefix and is not a valid IPv6 address.
The entire global-unicast IPv6 address range is from 2000::/128 to 3FFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF/128, resulting in a total usable space of over 42,535,295,865,117,307,932,921,825,928,971,000,000 addresses, which is only 1/8th of the entire IPv6 address space!

(C) IPv6 Questions by Chris Bryant

Chris Bryant has six practice IPv6 questions on his website at
http://www.thebryantadvantage.com/CCNACertificationPracticeExamIPVersion6.htm

His question 3  is related to the last question above
Question C- 3: What address type is indicated by the first 96 bits being set to zero?
Answer:
 That's an IPv4-compatible address.

MY NOTE: Question 7 of the 9tut.com questions asks you to select valid IP v6 addresses and lists  ::192:168:0:1 as one of them. Note the double colon :: at the beginning. This represents 96 bits set to zero leaving 32 bits for the IPv4 address which is incorporated into the IPv6 address. 

Question C- 6. Where will you find IPv6 addresses beginning with 2002 and carrying a /48 prefix?

A. 6to4 tunnel edge routers

B. loopback interfaces

C. 6to4 tunnel access routers

D. Any link-layer master router

E. Any site-local DR

Answer A: 6to4 tunnel edge routers - the IPv6 routers that are communicating with each other through the IPv4 cloud - carry an IPv6 address beginning with 2002, followed by their IPv4 address expressed in hex. They carry a /48 prefix.


(D) IPv6 Questions by Anthony Sequeira

www.stormwindlive.com 
Question D- 1. Name three benefits of IPv6. Choose 3. 
a. Decreased reliance on multicast
b. Elimination of broadcast behavior
c. Enhanced DHCP usage
d. Increased security features
e. IP address autoconfiguration
Answer: b, d, e

Question D- 2. Which two statements regarding a link-local address are true? Choose 2. 
a. A link-local address is manually configured when needed
b. A link-local address begins FE80 
c. A link-local address is assigned by the ISATAP tunnel process 
d. A link-local address is based upon an existing Layer 2 address
 Answer:  b, d


Question D- 3. What is the loopback address used in IPv6? Choose 2. 
a. 0:0:0:0:0:0:0:1
b. 1:1:1:1:1:1:1:1
c. 1::
d. ::1
Answer: a, d


Question D- 4. Which of the following is NOTa feature of Anycast addressing in IPv6?
a. Same IPv6 address assigned to multiple nodes
b. Routing protocol makes the “nearest” determination
c. Supports many future potential applications 
d. Provides an any-to-many communication model
Answer: d



(E) from book "CCNA Practice Questions" - Chapter 8

http://my.safaribooksonline.com/book/certification/ccna/9780768682427

(The book "CCNA Practice Questions" by Jeremy CCIE No. 11727 Cioara is published by Pearson Certification. Selections from it are available free - including the IPv6 questions and answers.)
Question E- 4. Which of the following are invalid IPv6 communication types? (Choose two.)
 A .Unicast 
B. Multicast 
C. Broadcast 
D. Anycast 
E. Cryptocast

Answer: C, E.  IPv6 uses three types of communication: Unicast (one-to-one), Multicast (one-to-many), and Anycast (one-to-closest). Answer C is incorrect because the concept of Broadcast messaging is tied with the IPv4 protocol and is no longer valid in IPv6. Answer E is incorrect because there is no such thing as Cryptocast messaging.

Question E- 5. Which of the following are valid IPv6 addresses? (Choose three.)
A. 2001:0db8:0000:0000:0000:0000:1428:57ab
B. 2001:0db8::1428:57ab
C. 2001::1685:2123::1428:57ab
D. 2001:99:ab:1:99:2:1:9
E. 2001:1428:57ab:1685:2123:1428:57ab
Answer: A, B, D. An IPv6 address consists of eight sets that can be four hexadecimal characters each. Consecutive sets of zeros can be abbreviated with a double colon (::), but this can only be used once in each IP address. Leading zeros can also be dropped. Based on these rules, addresses from the question can be described as:

2001:0db8:0000:0000:0000:0000:1428:57ab (Valid, eight sets)
2001:0db8::1428:57ab (Valid, same address as above with abbreviation)
2001::1685:2123::1428:57ab (Invalid use of double colon)
2001:99:ab:1:99:2:1:9 (Valid, dropped leading zeros)
2001:1428:57ab:1685:2123: 1428:57ab (Invalid, only seven sets)

Question E- 18. In IPv6, Internet-valid addresses are known by what name? 
A. Private 
B. Public 
C. Unique 
D. Unspecified 
E. Global

Answer: E. The Internet-valid addresses are considered “global” addresses in IPv6. They are specified to begin with 2000::/3. Answer A is incorrect because private addresses are for use in a private network, as it currently happens in IPv4 addressing. Answer B is incorrect because global addresses have replaced public addresses. Answers C and D do not apply directly to IPv6 addressing.

Question E- 19. In IPv6, a ___________ address is used to communicate with hosts on the directly attached network and will never forward beyond the first router hop. 
A. Global 
B. Private 
C. Link local 
D. Private restricted 
E. Auto-generated
Answer: C. Link-local addressing is a new concept when moving from IPv4 to IPv6. Link-local addresses are used to communicate directly on a link. This is used for communication such as establishing OSPF neighbor relationships or sending RIP routes. Answer A is incorrect because global addresses can access the Internet directly. Answer B is incorrect because private IPv6 addresses can route through an organization. The addresses shown in answers D and E do not exist in the IPv6 environment.

Question E- 20. Which of the following commands could you use to assign an IPv6 address to your router? 

A .Router(config-if)#ip address fe01:3112:abcd::0001 255.255.255.0 
B .Router(config-if)#ip address fe01:3112:abcd::0001/48 
C .Router(config-if)#ip address 6 fe01:3112:abcd::0001 255.255.255.0 
D. Router(config-if)#ip address 6 fe01:3112:abcd::0001/48 
E. Router(config-if)#ipv6 address fe01:3112:abcd::0001 255.255.255.0 
F. Router(config-if)#ipv6 address fe01:3112:abcd::0001/48

Answer: F. IPv6 addresses are assigned using the ipv6 address command. In IPv6, there is no decimal version of the subnet mask; all subnet masks are written in bit-notation. Answers A, C, and E are incorrect because they use the decimal version of the subnet mask. Answers B and D are incorrect because they use the incorrect command.


Question E- 21 Which of the following commands could you use to start a RIPng process on your router? 

A. Router(config)#router RIPng 
B. Router(config)#ipv6 router rip RIPTagNo1 
C. Router(config)#routerv6 RIP 
D. Router(config)#ripv6

Answer B. The exact syntax to enable the RIPng (RIP for IPv6) routing protocol is ipv6 router rip <tag>. The tag can be anything from a number to a name; in this question, the tag was “RIPTagNo1”. This tag must be used when enabling RIP on an interface-by-interface basis. Answers A, C, and D will produce invalid syntax messages.


Question E-30. Which of the following commands enables the IPv6 protocol on a router? 
A. Router(config)#ipv6 unicast-routing 
B. Router(config)#ipv6 enable 
C. Router(config)#enable ipv6 
D. Router(config)#ipv6 
E. Router(config)#router ipv6

Answer: A. To enable the IPv6 protocol, use the command ipv6 unicast-routing from global configuration mode. All other answers produce an invalid syntax or incomplete command message.


(F) Miscellaneous

The following are two  questions from the Cisco CCNA Discovery course
Question F-1 Refer to the following command
RouterX (config-if) IPv6 address 2001:DB8:2222:7272::72/64
Which statement is true?

Answer: The complete IPv6 address is manually specified for the interface.
[My Note: This is a normal Global Unicast IPv6 address with a network prefix of 64 bits. In full it would be:
2001:0DB8:2222:7272:0000:0000:0000:0072/64 ]


Question F-2 What are two ways that some networks can use IPv6 addreses and still communicate over the Internet with their other networks that use IPv4 (choose two)?

The answers are:
Enable tunneling to allow IPv6 packets to be encapsulated and travel over IPv4 networks AND
Upgrade the IOS image on the IPv6 edge routers to an image that can translate IPv6 packets to IPv4 packets.

IPv6 Address Representation


General

Some of the following is from the Cisco Networking Academy CCNA Discovery course (Semester 4 - Designing and Supporting Computer Networks, Chapter 6). This is the course we followed in College but it is probably too expensive for private study!

An IPv6 address is 128 bits or 16 bytes long : 4 times the bits of IPv4

The IPv6 address is displayed as 32 Hexadecimal digits - divided into 8 blocks of 4 digits each.

The format is
X:X:X:X::X:X:X:X where each X is a 16-bit hexadecimal field.

Note that:
Hexadecimal A, B, C, D, E, F can be written as a, b, c, d, e, f.
Leading zeros in a field are optional AND
Successive fields of zeros can be displayed as a double-colon  ::  - but only once for each address

EXAMPLES:
2031:0000:130F:0000:0000:09C0:876A:130B
can be represented as 2031:0:130f::9c0:876a:130b. (This is a UNICAST address - the main type of IPv6 address)

FF01:0:0:0:0:0:0:1  can be represented as FF01::1 (This is a MULTICAST address.)
0:0:0:0:0:0:0:1      = =        ::1   (this is the IPv6 LOOPBACK address)
0:0:0:0:0:0:0:0      = =         ::    (UNSPECIFIED address e.g. used by a device before it gets its first proper IPv6 address)

UNICAST sends packets to one specific device with one specific address. This is the main type of IPv6 address.

Format of Global Unicast Address:
All Global unicast addresses begin with 2000::/3.  What does this mean? It means that the first 3 Binary Bits (out of 128 bits) are the most significant AND that the first 3 bits must match the value in hex 2000.
Hex 2 = Binary 0010
Hex 0 = Binary 0000
Therefore the Hex field 2000 is the equivalent of Binary 0010 0000 0000 0000
The first 3 bits MUST be 001. Therefore the first 4 bits can be either 0010 OR 0011
Thus a Global Unicast address can start with Hex digit 2 OR Hex digit 3.

Therefore the entire global-unicast IPv6 address range begins at
2000:0000:0000:0000:0000:0000:0000:0000/128 (or 2000::/128 for short)
and ends at
3FFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF/128

Almost all the Global IPv6 address that I have seen mentioned in books, begin with Hex 2. Perhaps the Hex 3s have not yet been issued?

Multicast and Anycast but NO Broadcast
There are NO Broadcast address in IPv6. Their role has been taken over by Multicast addresses and - to a lesser extent - by Anycast addresses:

  • MULTICAST sends a packet to every member of a group. It is a One-to-Many type of address.
  • ANYCAST  addresses send a packet to any one member of the group of devices that has an anycast address assigned. For efficiency, a packet that is sent to an anycast address is delivered to the closest interface. For that reason, anycast can also be thought of as a One-to-Nearest type of address. (Anycast addresses can be used for things like the nearest DNS server or the  nearest DHCP server etc. The address is allocated to a group of servers but the packet is only delivered to the nearest one.)        

Global and Reserved Addresses

The basic types of IPv6 unicast addresses are:
  • Global
  • Reserved (private, loopback, unspecified)   
 The IPv6 Global Unicast Address is the equivalent of an IPv4 registered public address i.e. one that can be used on the Internet.   An example is
2001:99:ab:1:99:2:1:9/64   (leading zeros have been dropped).

Unicast and anycast addresses are typically composed of two logical parts: a 64-bit network prefix used for routing, and a 64-bit interface identifier used to identify a host's network interface.

One method for IPv6 global unicast address assignment is that
  • The Internet Corporation for Assigned Network Numbers (ICANN) allocates large address blocks to Regional Internet Registries (RIRs), 
  • RIRs assign smaller address blocks to Internet Service Providers (ISPs) and 
  • ISPs assign even smaller address blocks to their customers.               
The 64 bit  prefix consists of a  Routing Prefix which comes from the address elements assigned by ICANN, the RIR and the ISP plus a Subnet Prefix assigned by the enterprise that requested the IPv6 address. Typically
  • ICANN assigns the first 12 bits of the Routing prefix
  • the Regional Internet Registry assigns the next 20 bits
  • the ISP assigns the next 16 bits.
This gives a total of 48 bits for the Routing Prefix. Therefore the enterprise can use the next 16 bits as the Subnet Prefix giving a total prefix length of 64 bits. This allows for 2 to the power of 16 subnets - a huge number.

General unicast address format (routing prefix size varies)
bits
48 (or more)
16 (or fewer)
64
field
routing prefix
subnet id
interface identifier
(illustration from the Wikipedia article "IPv6 Address")
http://en.wikipedia.org/wiki/IPv6_address

The allocation of prefix bits may be different from the above e.g. the ISP may take extra bits which means that the enterprise will have less bits for subnetting purposes. However the prefix for a Global Unicast address is almost always 64. Thus the number of bits for the interface ID will also be 64.
NOTE: For one exception see Question C-6 of my "IPv6 Questions and Answers for CCNA Exam"
http://ccnaexam4dummies.blogspot.ie/2012/08/ipv6-questions-and-answers-for-ccna-exam_2435.html

Note re Anycast Address: The format of the Anycast address is the same as that for the  Global Unicast Address. The difference is that the same  Anycast address can be used for a number of different devices!

Reserved Unicast Addresses:

Like IPv4, a block of IPv6 addresses is set aside for private addresses.

Below is the list of common kinds of IPv6 Reserved addresses:
Unspecified address::0 This is used before the interface receives its first
normal IPv6 address
Loopback address::1 This is the equivalent of the IPv4 address 127.0.0.1
It is used to check if the network interface is working
(Ping ::1 to check)
Link Local AddressAssigned with FE80::/64 prefix. Intended for communication within a segment of the local network or for point to point communication. Closest equivalent in IPv4 is 169.254.0.0/16 (this is used in IPv4 when a PC cannot get IP address because DHCP server is out of order.) Every IPv6 devise MUST have a Link Local address.
Unique Local AddressAssigned with FD00::/8 prefix . It is the approximate IPv6 equivalent of the IPv4 Private Addresses (10.0.0.0/8, 172.16.0.0/16 etc). Intended for use in private networks e.g. within a single site or organisation or spanning a limited number of sites/organisations. Not routable on the Internet. This replaces the obsolete Site Local Address.
Site Local Address (obsolete)The site local prefix FEC0::/10 was originally allocated for addresses within the site network of an organisation i.e. it was intended to be the equivalent of IPv4 Private addresses. However problems arose with its use and it has been replaced by the Unique Local Address system.

NOTE: What does FD00::/8 mean? Well the prefix is 8 which means that the first 8 binary bits (out of 128 binary bits) are the most significant AND the first 8 bits must match the value in Hex FD00
Hex F = Binary 1111   (the decimal equivalent is 15)
Hex D = Binary 1101  (the decimal equivalent is 13)
Therefore the first 8 binary bits of a Unique Local Address are
1111 1101

EUI-64 Format for IPv6 addresses

One of IPv6's key benefits over IPv4 is its capability for automatic interface addressing. By implementing the IEEE's 64-bit Extended Unique Identifier (EUI-64) format, a host can automatically assign itself a unique 64-bit IPv6 interface identifier without the need for manual configuration or DHCP. This is done by using  the already unique 48-bit MAC address, and adding inserting a further 16 bits in order to arrive at the 64 bits needed for  the interface part of the 128-bit IPv6 address.

The main step is to convert the 48-bit MAC address to a 64-bit value. To do this, we break the MAC address into its two 24-bit halves: the Organizationally Unique Identifier (OUI) and the NIC specific part. The 16-bit hex value FFFE is then inserted between these two halves to form a 64-bit address.
For example take a MAC address 00:12:7F:EB:6B:40 which can also be written as 0012:7FEB:6B40 . The first 6 Hexadecimal digits of the MAC are the OUI and the second six are the NIC specific part. The MAC address is turned into a 64-bit EUI-64 by inserting FFFE in the middle. Thus we get 0012:7FFF:FEEB:6B40 as the interface portion of the IPv6 address. This is typically done both for the Link-Local address and the Global Unicast address for a specific interface. (Of course the Prefix for the two addresses will be completely different.)

Thus based on the above example you can have an interface that has
(a) a Link Local Address of FE80::0012:7FFF:FEEB:6B40/64 (prefix is FE80:: or FE80:0000:0000:0000 AND
(b) a Global Unique Address of say 2001:99:ab:1:0012:7FFF:FEEB:6B40/64 (Prefix is 2001:99:ab:1 )

The following illustration is from an article by Jeremy Stretch of PacketLife.net
EUI-64 in IPv6 You will note from his article that the EUI-64 process is slightly more complex than I have set out above. However for CCNA exam purposes, it should be enough for you to recognise an EUI-64 address and understand how it relates to the MAC address.

eui64_step1.png

Multicast Addresses


Multicast Addresses in IPv6 have the prefix FF00::/8
What does this mean? Well the prefix is 8 which means that the first 8 binary bits (out of 128 binary bits) are the most significant and must match the value in Hex FF00
Hex F = Binary 1111
Hex 0 = Binary 0000
Therefore the first 8 bits of every IPv6 Multicast address are
1111 1111


Some Important IPv6 Multicast Addresses
FF02::1All Nodes on the local network segment. This is the closest IPv6 equivalent to the IPv4 Broadcast address and is NOT recommended as it uses up a lot of network resources.
FF02::2All Routers on the local network segment
FF02::9RIPng Routers. This is the IPv6 equivalent to the IPv4 Multicast address 224.0.0.9 that is used to send routing information to all RIPv2 Routers in a network segment. (Note the use of "9" in both multicast addresses.)

Note: It is often stated that the Broadcasts of IPv4 have been replaced by the Multicasts AND Anycasts of IPv6. Therefore you would think that an Anycast address should resemble a Multicast one. In fact the Anycast Addresses has the same format as the Glabal Unicast one.


Summary and Reminder for CCNA Exam

The following helped me to remember the differences between the various IPv6 addresses:

(i) An IPv6 Multicast Address begins with FF - the prefix is FF00::/8.
This should be easy to remember.Hex  FF is Binary 1111 1111. In IPv4 the binary number 11111111 translates into decimal 255 - a number that is often associated with Broadcast addresses.

Moving down the alphabet we come to FE.

(ii) An IPv6 Link Local Address begins with FE - the prefix is FE80::/64
The Link Local address is the most important IPv6 Private address. Every IPv6 enabled interface has one and it is automatically created by Stateless Autoconfiguration.

The name Link Local can explain the function of this address. It LINKS the IPv6 device to the LOCAL (in this case the NEXT) device only in one segment of a network  - for example it is used for  point to point communication between two Routers or between a Router and a PC.

Again moving down the alphabet we come to FD.

(iii) The Unique Local Address begins with FD - the prefix is FD::/8.
This is the next most important Private address. Not every IPv6 device has a Unique Local but it has the widest scope of any private address. It spans a single site or organisation or a number of related sites - but it is not routable on the Internet. (I compare this in my mind to the Global Unicast address that spans the entire Internet and ALSO has the letters "Uni" in its name! Well if it helps me to remember why not?)

(iv) Remember that the addresses :: (the unspecified address) and ::1(the loopback address ) are local to their own IPv6 device only. You can think of them as the opposite of the Unique Local address!



Transition from IPv4 to IPv6

Transition from IPv4 to IPv6

There are several ways to integrate an IPv6 structure into an existing IPv4 network. The transition from IPv4 to IPv6 does not have to be done all at once. The three most common transition methods are:
  • Dual stack
  • Tunneling
  • Proxying and translation
In the Dual Stack transition method, both IPv4 and IPv6 configurations are implemented on a network device. Both protocol stacks run on the same device. This method enables IPv4 and IPv6 to coexist.

Tunneling is a technique that is becoming more prominent as the adoption of IPv6 grows. Tunneling is the encapsulation of one protocol packet within another protocol. For example, an IPv6 packet can be encapsulated within an IPv4 protocol.

Cisco IOS Releases 12.3(2)T and later, include Network Address Translation-Protocol Translation (NAT-PT) between IPv6 and IPv4. This translation allows direct communication between hosts that use different versions of the IP protocol.

In relation to Tunneling techniques see question 5 in the www.9tut.com series of questions on IPv6http://www.9tut.com/ccna-ipv6


5. Which three of the following are IPv6 transition mechanisms? (Choose three)
A – 6to4 tunneling
B – GRE tunneling
C – ISATAP tunneling
D – Teredo tunneling
E – VPN tunneling
F – PPP tunneling
Answer: A C D
Below is a summary of IPv6 transition technologies:
6 to 4 tunneling: This mechanism allows IPv6 sites to communicate with each other over the IPv4 network without explicit tunnel setup. The main advantage of this technology is that it requires no end-node reconfiguration and minimal router configuration but it is not intended as a permanent solution.
ISATAP tunneling (Intra-Site Automatic Tunnel Addressing Protocol): is a mechanism for transmitting IPv6 packets over IPv4 network. The word “automatic” means that once an ISATAP server/router has been set up, only the clients must be configured to connect to it.
Teredo tunneling: This mechanism tunnels IPv6 datagrams within IPv4 UDP datagrams, allowing private IPv4 address and IPv4 NAT traversal to be used.
In fact, GRE tunneling is also a IPv6 transition mechanism but is not mentioned in CCNA so we shouldn’t choose it (there are 4 types of IPv6 transition mechanisms mentioned in CCNA; they are: manual, 6-to-4, Teredo and ISATAP).
[MY NOTE: For the CCNA exam, be sure that you can recognize the NAMES of the 3 main tunneling types i.e. 6 to 4ISATAP and Teredo ]

See also a question on Chris Bryant's website
Question 6:
Where will you find IPv6 addresses beginning with 2002 and carrying a /48 prefix?

A. 6to4 tunnel edge routers

B. loopback interfaces

C. 6to4 tunnel access routers

D. Any link-layer master router

E. Any site-local DR

Answer: A.
 6to4 tunnel edge routers - the IPv6 routers that are communicating with each other through the IPv4 cloud - carry an IPv6 address beginning with 2002, followed by their IPv4 address expressed in hex. They carry a /48 prefix.
  

The following is a question from the Cisco CCNA Discovery course:
What are two ways that some networks can use IPv6 addreses and still communicate over the Internet with their other networks that use IPv4 (choose two)?

The answers are:
Enable tunneling to allow IPv6 packets to be encapsulated and travel over IPv4 networks AND
Upgrade the IOS image on the IPv6 edge routers to an image that can translate IPv6 packets to IPv4 packets.


For main post on "IPv6 and IPve - Differences between them (for CCNA Exam" see

http://ccnaexam4dummies.blogspot.ie/2012/08/ipv6-and-ipv4-differences-between-them.html

TO BE CONTINUED