Home > IPv6 Questions 4

IPv6 Questions 4

July 20th, 2017 in ROUTE 300-101 Go to comments

Question 1

Question 2

Question 3


An automatic 6to4 tunnel allows isolated IPv6 domains to be connected over an IPv4 network to remote IPv6 networks. The key difference between automatic 6to4 tunnels and manually configured tunnels is that the tunnel is not point-to-point; it is point-to-multipoint -> it allows multiple IPv4 destinations -> B is correct.

A is not correct because manually 6to4 is point-to-point -> only allows one IPv4 destination.

Configuring 6to4 (manually and automatic) requires dual-stack routers (which supports both IPv4 & IPv6) at the tunnel endpoints because they are border routers between IPv4 & IPv6 networks.

(Reference: http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-tunnel_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1055515)

Question 4

Question 5


In fact this question has no correct answer. The IPv6 EUI-64 format address is obtained through the 48-bit MAC address. The MAC address is first separated into two 24-bits, with one being OUI (Organizationally Unique Identifier) and the other being NIC specific. The 16-bit 0xFFFE is then inserted between these two 24-bits to for the 64-bit EUI address. IEEE has chosen FFFE as a reserved value which can only appear in EUI-64 generated from the an EUI-48 MAC address.

For example, the MAC address C601.420F.0007 is divided into two 24-bit parts, which are “C60142” (OUI) and “0F0007” (NIC). Then “FFFE” is inserted in the middle. Therefore we have the address: C601.42FF.FE0F.0007.

Question 6


6to4 tunnel is a technique which relies on reserved address space 2002::/16 (you must remember this range). These tunnels determine the appropriate destination address by combining the IPv6 prefix with the globally unique destination 6to4 border router’s IPv4 address, beginning with the 2002::/16 prefix, in this format:


For example, if the border-router-IPv4-address is, the tunnel interface will have an IPv6 prefix of 2002:C0A8:6301::/64, where C0A8:6301 is the hexadecimal equivalent of

Question 7

  1. BG
    August 6th, 2017

    For Question 2, isn’t a solicitation when the client or host sends out a message to find out if there is a DHCP server available that can support its requests?

  2. mago
    November 4th, 2017
  3. Beagle
    March 31st, 2018

    Q5, my impression is EUI-64 is calculated on the Link-Local address, which consists of the MAC address.

  4. unstoppable
    April 15th, 2018

    Ya if the Q5 come out, I will chose link-local address too

  5. Anonymous
    June 6th, 2018

    Agree on q5. I would have chosen link-local.

  1. No trackbacks yet.