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IPv6 Questions 2

August 7th, 2015 in ROUTE 300-101 Go to comments

Question 1

Question 2

Question 3

Explanation

Address Family Translation (AFT) using NAT64 technology can be achieved by either stateless or stateful means:
+ Stateless NAT64 is a translation mechanism for algorithmically mapping IPv6 addresses to IPv4 addresses, and IPv4 addresses to IPv6 addresses. Like NAT44, it does not maintain any bindings or session state while performing translation, and it supports both IPv6-initiated and IPv4-initiated communications.
+ Stateful NAT64 is a stateful translation mechanism for translating IPv6 addresses to IPv4 addresses, and IPv4 addresses to IPv6 addresses. Like NAT44, it is called stateful because it creates or modifies bindings or session state while performing translation. It supports both IPv6-initiated and IPv4-initiated communications using static or manual mappings.

Reference: http://www.cisco.com/c/en/us/products/collateral/ios-nx-os-software/enterprise-ipv6-solution/white_paper_c11-676278.html

Question 4

Question 5

Explanation

When a change is made to one of the IP header fields in the IPv6 pseudo-header checksum (such as one of the IP addresses), the checksum field in the transport layer header may become invalid. Fortunately, an incremental change in the area covered by the Internet standard checksum [RFC1071] will result in a well-defined change to the checksum value [RFC1624]. So, a checksum change caused by modifying part of the area covered by the checksum can be corrected by making a complementary change to a different 16-bit field covered by the same checksum.

Reference: https://tools.ietf.org/html/rfc6296

Question 6

Question 7

Explanation

Link-local addresses are always configured with the FE80::/64 prefix. Most routing protocols use the link-local address for a next-hop.

Question 8

Explanation

A link-local address is an IPv6 unicast address that can be automatically configured on any interface using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64 format. Link-local addresses are not necessarily bound to the MAC address (configured in a EUI-64 format). Link-local addresses can also be manually configured in the FE80::/10 format using the ipv6 address link-local command.

Reference: http://www.cisco.com/c/en/us/support/docs/ip/ip-version-6-ipv6/113328-ipv6-lla.html

Question 9

Explanation

Stateless Address Auto Configuration (SLAAC) is a method in which the host or router interface is assigned a 64-bit prefix, and then the last 64 bits of its address are derived by the host or router with help of EUI-64 process.

Question 10

Question 11

Explanation

The components of IPv6 header is shown below:

IPv6_header.jpg

The Traffic Class field (8 bits) is where quality of service (QoS) marking for Layer 3 can be identified. In a nutshell, the higher the value of this field, the more important the packet. Your Cisco routers (and some switches) can be configured to read this value and send a high-priority packet sooner than other lower ones during times of congestion. This is very important for some applications, especially VoIP.

The Flow Label field (20 bits) is originally created for giving real-time applications special service. The flow label when set to a non-zero value now serves as a hint to routers and switches with multiple outbound paths that these packets should stay on the same path so that they will not be reordered. It has further been suggested that the flow label be used to help detect spoofed packets.

The Hop Limit field (8 bits) is similar to the Time to Live field in the IPv4 packet header. The value of the Hop Limit field specifies the maximum number of routers that an IPv6 packet can pass through before the packet is considered invalid. Each router decrements the value by one. Because no checksum is in the IPv6 header, the router can decrease the value without needing to recalculate the checksum, which saves processing resources.

Question 12

Explanation

We need to summarize three IPv6 prefixes with /64 subnet mask so the summarized route should have a smaller subnet mask. As we can see all four answers have the same summarized route of 2001:DB8:: so /48 is the best choice.

Note: IPv6 consists of 8 fields with each 16 bits (8×16 = 128).

Comments
  1. Dereje
    February 27th, 2015

    NTPv6 means a Network Prefix Translation of IPv6
    some times there a need to translate from one IPv6 subnet/prefix (like site local/LAN) to some kind of Global routing prefix. I think so.

  2. help
    April 26th, 2015

    can i get some explanation on questions q2 and q5? i dont think that i understand them and the answers.
    thanks

  3. Prezes
    April 27th, 2015

    Q5:

    “C” – Correct
    https://tools.ietf.org/html/rfc6296#page-3

    1.2. NPTv6 Applicability

    NPTv6 provides a simple and compelling solution to meet the address-independence requirement in IPv6. The address-independence benefit stems directly from the translation function of the network prefix translator. To avoid as many of the issues associated with NAPT44 as possible, NPTv6 is defined to include a two-way, checksum-neutral, algorithmic translation function, and nothing else.

  4. ill
    June 24th, 2015

    Prezes, your explanation is very good and accurate. What I wonder is how are we supposed to study all RFCs and cisco.com documents if such specific information is not on the Cisco Press books …

  5. digitaltut
    July 24th, 2015

    @all: Because of copyrighted issue, we had to remove all the questions and answers. We can only keep the explanations. You can download all the questions and answers at: https://mega.co.nz/#!0pUxSZoJ!s293gEdQu4xLndoA7zZTq5ldia3gdZlrZqNxc_AgpFc
    or
    http://www.4shared.com/office/-GBRNxjKce/ROUTE_July_2015.html

  6. Sahil
    July 28th, 2015

    I am not able to see the questions admin? Please help. Its only showing the explanation.

  7. Cristina
    August 31st, 2015

    I also have the same problem….why?

  8. Deeez
    September 30th, 2015

    Can someone explain Question 11? Isn’t Source and Destination IP the ususal way to identify packets for filtering?

  9. Aditya
    October 11th, 2015

    hii all,
    Q11–should be a /60 ??

    2001:db8:0:7::
    2001:db8:0:8::
    2001:db8:0:9::

    we have the common portion as 2001:db8:0:000 (uncommon hex digit here)

    that makes (note the abbreviated ipv6 notation-ipv6 is combin of 8 sets of 4 hex symbols)

    (4 hex symb X 3 full sets)+ 3 hex symb =15 hex symb

    15 hex symb X 4 bits/symbol =60 bits

    (hex–binary
    7—-0111
    8—–1000
    9—–1001

    no common BITS here)

    so its a /60

    Pls correct me if I am wrong..

  10. Anonymous
    October 28th, 2015

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  11. Anonymous
    December 29th, 2015

    I’m confused about the answers listed for #9. Why wouldn’t it be B and C? SLAAC and DHCPv6 seem like better answers for dynamic IPv6 addressing mechanisms. I thought EUI-64 was just a format.

  12. vic
    January 14th, 2016

    The go to this place: goo.gl/vroZC5

  13. radix
    January 25th, 2016

    Q11 seems to be plain wrong from the beginning, because of the way it’s asked and the answers it expects. As Cisco explains in one article about IPv6 security:

    “IPv6 Packet Inspection

    The following IPv6 header fields are all used for IPv6 inspection: traffic class, flow label, payload length, next header, hop limit, and source and destination addresses. For further information about IPv6 header fields, see RFC 2474, Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers.

    Which makes it clear that there are 5 correct answers (Traffic Class, Source Address, Flow Label, Hop Limit and Dest. Address) and not 3.

    Link to article: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/sec_data_cbac_fw/configuration/15-mt/sec-data-cbac-fw-15-mt-book/ip6-firewall.html

  14. eth0
    February 26th, 2016

    @Radix,

    just read through your link. you make not just a good point, but possibly a good case for a future D&D question. I happen to agree with your assessment. maybe the question should read “choose all that apply”.

    good catch.

  15. eth0
    February 26th, 2016

    @Radix again, granted i am NOT an IPv6 nor security expert but maybe there is something in the weeds we are overlooking with the last section of the question “in order to filter futer attacks.” I am putting a lot of time reading the linked white papers from this site, studying under KWallace and his livelessons, as well as JeremyC. if I find something definitive, ill post.

  16. q11
    March 15th, 2016

    Attack techniques
    A denial-of-service attack is characterized by an explicit attempt by attackers to prevent legitimate users of a service from using that service. There are two general forms of DoS attacks: those that crash services and those that flood services.
    The most serious attacks are distributed and in many or most cases involve forging of IP sender addresses (IP address spoofing) so that the location of the attacking machines cannot easily be identified, nor can filtering be done based on the source address.
    source: https://en.wikipedia.org/wiki/Denial-of-service_attack

  17. q11
    March 15th, 2016

    Also there is no point to filter by destination address, because it will filter all traffic.

  18. Mary
    May 28th, 2016

    If you are looking for premium dumps, send an email @ premiumdumps@zoho(dot)com whit the exam code.

  19. kaunglay
    July 12th, 2016

    Please give me a answer in the following IPv6 Question .

    Which two statements are true about 6to4 tunnels? (Choose two.)

    A. In a 6to4 tunnel, the first two bytes of the IPv6 address will be 0?002 and the next four bytes will be the hexadecimal equivalent of the IPv4 address.
    B. In a 6to4 tunnel, the first two bytes of the IPv6 address will be locally derived and the next two bytes will be the hexadecimal equivalent of the IPv4 address.
    C. In a 6to4 tunnel, the IPv4 address 192.168.99.1 would be converted to the 2002:c0a8:6301::/48 IPv6 address.
    D. In a 6to4 tunnel, the IPv4 address 192.168.99.1 would be converted to the 2002:c0a8:6301::/16 IPv6 address.
    E. In a 6to4 tunnel, the IPv4 address 192.168.99.1 would be converted to the 2002:1315:4463:1::/64 IPv6 address.

  20. Anonymous
    August 11th, 2016

    the answer is 2002:c0a8:6301::/48 because convert 192 i.e. it becomes 11000000 now divide it into 2 groups …. 1100 0000 now put the power starting from right separately for the two groups. i.e. 1100 —- 1(power8) 1(power 4) 0(power2) 0(power1) now when you get the result its 8 4 0 0 add them up its 12. What is 12 in hex ? 12 = c you have your c there now do this for all else of the ipv4.

  21. Mina
    August 15th, 2016

    I’d verntue that this article has saved me more time than any other.

  22. cahh
    September 9th, 2016

    For Q11 I think it refers to the fact that what are the headers that can be matched for IPv6 that can not also be matched for IPv4.

    So knowing that Traffic Class, Source Address, Flow Label, Hop Limit and Dest. Address are valid IPv6 Headers, then the only ones that are different from IPV4 headers and exclusive for IPv6 are Traffic Class, Flow Label and Hop Limit.

    Source Address and Dest. Address are also IPv4 headers.

    Hope this helps.

  23. cahh
    September 9th, 2016

    forgot to add a reference from Cisco to see the headers from both IPV4 and IPV6 for comparison:

    http://www.cisco.com/en/US/technologies/tk648/tk872/technologies_white_paper0900aecd8054d37d.html

  24. ASM
    September 13th, 2016

    If You need more hands on Lab on IPv6 OSPF (V3) ; please check out this link with Video and PDF of the commands. http://asmed.com/cisco-ccna-ospf-ipv6-configuration/ . Good Luck on your exam.

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    November 17th, 2016

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