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IPv6 Questions 3

July 20th, 2019 in ROUTE 300-101 Go to comments

Question 1


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). All the above prefix starts with 2001:DB8:0 (16 bits x 3 = 48) so we need at least /48 mask to summarize them.

Question 2

Question 3

Question 4


DHCPv6 can be implemented in two ways : Rapid-Commit and Normal Commit mode. In Rapid-Commit mode , the DHCP client obtain configuration parameters from the server through a rapid two message exchange (solicit and reply).

The “solicit” message is sent out by the DHCP Client to verify that there is a DHCP Server available to handle its requests.

The “reply” message is sent out by the DHCP Server to the DHCP Client, and it contains the “configurable information” that the DHCP Client requested.

Just for your information, in Normal-Commit mode, the DHCP client uses four message exchanges (solicit, advertise, request and reply). By default normal-commit is used.

Question 5


The IPv6-to-IPv6 Network Prefix Translation (NPTv6) provides a mechanism to translate an inside IPv6 source address prefix to outside IPv6 source address prefix in IPv6 packet header and vice-versa. In other words, NPTv6 is simply rewriting IPv6 prefixes. NPTv6 does not allow to overload. It does not support mismatching prefix allocations sizes (so the network/host portion remains intact. For example you cannot cover /64 to /48).

Question 6

Question 7

Question 8

Question 9


The automatic tunneling mechanism uses a special type of IPv6 address, termed an “IPv4-compatible” address. An IPv4-compatible address is identified by an all-zeros 96-bit prefix, and holds an IPv4 address in the low-order 32-bits. IPv4-compatible addresses are structured as follows:


Therefore, an IPv4 address of will be written as :: or 0:0:0:0:0:0: or ::0A43:0002 (with 10[decimal] = 0A[hexa] ; 67[decimal] = 43[hexa] ; 0[hexa] = 0[decimal] ; 2[hexa] = 2[decimal])

Question 10

  1. Maineah
    August 5th, 2017

    Shouldn’t question 5 be A and F according to your explanation?

    > It does not support mismatching prefix allocations sizes

  2. Maineah
    August 5th, 2017

    Sorry I meant C and F

  3. Paco
    November 3rd, 2017

    Q1 I dont understand why the right answer isn’t C, I mean the more sumarized the better right? so /32 would be better or also valid. Please help me see if I am missing something

  4. aa
    December 18th, 2017

    2001 :DB8: 0 :: /48
    16 + 16 + 16 = 48

  5. tell
    January 9th, 2018

    A major benefit associated with NPTv6 is the fact that it avoids the requirement for an NPTv6 Translator to rewrite the transport layer headers which reduces the load on network devices. NPTv6 also does not interfere with encryption of the full IP payload.

  6. John McDoe
    January 23rd, 2019

    @Maineah August 5th, 2017

    No, more summarized is worse. This is a networking practice, try to summarize only what you need and not more. If you summarize too big (2000::/3), you’ll lose the ability to make routing decisions on a granular level.

  7. mac
    August 30th, 2019

    6RD = IPv6 Rapid Deployment
    6VPE = IPv6 VPN provider edge
    DS-Lite = Dual Stack Lite
    Dual-Stack IPv4-IPv6

    The transitions methods fall into three categories:

    – Dual-Stack
    – Encapsulation (6RD, 4RD, DS-Lite, A+P, 6PE, 6VPE)
    – Translation (NAT64, DNS64, dIVI, dIVI-pd, NAT444, NAT464)

  8. dave
    September 29th, 2019

    Q5: answer E “1-to-1 prefix rewrite” is valid.

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