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IPv6 Questions 2

October 28th, 2018 Go to comments

Note: If you are not sure about IPv6, please read our IPv6 tutorial.

Question 1


IPv6 router advertisement message is one type of the ICMPv6 packets with Type field value of 134. It lists many facts, including the link-local IPv6 address of the router. Normally, it is sent to the all-IPv6-hosts local-scope multicast address of FF02::1. When sent in response to router solicitation messages (ICMPv6 Type 133), it flows back to either the unicast address of the host that sent the RS or to the all-IPv6-hosts address FF02::1.

The advertised IPv6 prefix length must be 64 bits for the stateless address autoconfiguration to be operational.

Question 2


Below is the list of common kinds of IPv6 addresses:

Loopback address ::1
Link-local address FE80::/10
Site-local address FEC0::/10 (but it is deprecated and replaced with FC00::/7 for used in private networks)
Global address 2000::/3
Multicast address FF00::/8

Question 3


The “show ipv6 route” displays the current contents of the IPv6 routing table. This device is running OSPF so we can deduce it is running OSPFv3 (OSPF for IPv6). An example of the “show ip v6 route” is shown below:


Question 4


To run IPv6 on an interface we have to configure an IPv6 on that interface somehow -> A is correct.

IPv6 must be enabled first but with the “ipv6 unicast-routing”, not “ipv6 enable” command -> D is not correct.

Question 5


According to the official IANA website “Users are assigned IP addresses by Internet service providers (ISPs). ISPs obtain allocations of IP addresses from a local Internet registry (LIR) or National Internet Registry (NIR), or from their appropriate Regional Internet Registry (RIR): https://www.iana.org/numbers

Question 6


An example of configuring RIPng (similar to RIPv2 but is used for IPv6) is shown below:

Router(config)#ipv6 unicast-routing (Enables the forwarding of IPv6 unicast datagrams globally on the router)
Router(config)#interface fa0/0
Router(config-if)#ipv6 rip 9tut enable (9tut is the process name of this RIPng)

Question 7


Floating static routes are static routes that have an administrative distance greater than the administrative distance (AD) of another static route or dynamic routes. By default a static route has an AD of 1 then floating static route must have the AD greater than 1 -> Answer A is correct as it has the AD of 201.

Question 8


Directly connected routes: In directly attached static routes, only the output interface is specified. The destination is assumed to be directly attached to this interface, so the packet destination is used as the next-hop address. This example shows such a definition:

ipv6 route 2001:DB8::/32 gigabitethernet1/0/0

The example specifies that all destinations with address prefix 2001:DB8::/32 are directly reachable through interface GigabitEthernet1/0/0.

Recursive Static Routes: In a recursive static route, only the next hop is specified. The output interface is derived from the next hop. This example shows such a definition:

ipv6 route 2001:DB8::/32 2001:DB8:3000:1

This example specifies that all destinations with address prefix 2001:DB8::/32 are reachable via the host with address 2001:DB8:3000:1.

Fully Specified Static Routes: In a fully specified static route, both the output interface and the next hop are specified. This form of static route is used when the output interface is a multi-access one and it is necessary to explicitly identify the next hop. The next hop must be directly attached to the specified output interface. The following example shows a definition of a fully specified static route:

ipv6 route 2001:DB8:/32 gigabitethernet1/0/0 2001:DB8:3000:1

A fully specified route is valid (that is, a candidate for insertion into the IPv6 routing table) when the specified IPv6 interface is IPv6-enabled and up.

Besides three of the static IPv routes, there is one more type of IPv6 static route, that is Floating Static Routes (static route with a higher administrative distance than the dynamic routing protocol it is backing up)

For more information about these IPv6 routes, please read: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6/configuration/xe-3s/ipv6-xe-36s-book/ip6-stat-routes.html

Question 9


IPv6 includes two different unicast address assignments:
+ Global unicast address
+ Link-local address

The global unicast address is globally unique in the Internet. The example IPv6 address that is shown below is a global unicast address.


+ Site prefix (global routing prefix): defines the public topology of your network to a router. You obtain the site prefix for your enterprise from an ISP or Regional Internet Registry (RIR).
+ Site Topology and Subnet ID: the subnet ID defines an administrative subnet of the network and is up to 16 bits in length. You assign a subnet ID as part of IPv6 network configuration. The subnet prefix defines the site topology to a router by specifying the specific link to which the subnet has been assigned
+ Interface ID: identifies an interface of a particular node. An interface ID must be unique within the subnet.

Reference: https://docs.oracle.com/cd/E23823_01/html/816-4554/ipv6-overview-10.html

Question 10


A IPv6 Unique Local Address is an IPv6 address in the block FC00::/7. It is the approximate IPv6 counterpart of the IPv4 private address. It is not routable on the global Internet.

Note: In the past, Site-local addresses (FEC0::/10) are equivalent to private IP addresses in IPv4 but now they are deprecated.

Comments (11) Comments
  1. Confused
    March 9th, 2017

    I don’t get the last question 11, it says that Unique local addresses begin with 7 bits but I see 6 “On” bits on answer B, can someone explain please??

  2. aquaman
    March 13th, 2017

    In response to question 4
    What is one requirement for interfaces to run IPv6?
    A. An IPv6 address must be configured on the interface.
    B. An IPv4 address must be configured.
    C. Stateless autoconfiguration must be enabled after enabling IPv6 on the interface.
    D. IPv6 must be enabled with the ipv6 enable command in global configuration mode.

    Answer D is also right i suppose,

    Source : http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_55_se/configuration/guide/scg3750/swipv6.html#13205

    Step 1
    configure terminal
    Enter global configuration mode.
    Step 2
    sdm prefer dual-ipv4-and-ipv6 { default | routing | vlan } [ desktop ]
    Select an SDM template that supports IPv4 and IPv6.
    default —Set the switch to the default template to balance system resources.
    routing —Set the switch to the routing template to support IPv4 and IPv6 routing, including IPv4 policy-based routing.
    vlan —Maximize VLAN configuration on the switch with no routing supported in hardware.
    desktop —Supported only on Catalyst 3750-12S aggregator switches to set the switch to one of the desktop templates. If not selected on an aggregator switch, an aggregator template is automatically selected.
    Step 3
    Return to privileged EXEC mode.
    Step 4
    Reload the operating system.
    Step 5
    configure terminal
    Enter global configuration mode after the switch reloads.
    Step 6
    interface interface-id
    Enter interface configuration mode, and specify the Layer 3 interface to configure. The interface can be a physical interface, a switch virtual interface (SVI), or a Layer 3 EtherChannel.
    Step 7
    no switchport
    Remove the interface from Layer 2 configuration mode (if it is a physical interface).
    Step 8
    ipv6 address ipv6-prefix/prefix length eui-64
    ipv6 address ipv6-address link-local
    ipv6 enable
    Specify a global IPv6 address with an extended unique identifier (EUI) in the low-order 64 bits of the IPv6 address. Specify only the network prefix; the last 64 bits are automatically computed from the switch MAC address. This enables IPv6 processing on the interface.
    Specify a link-local address on the interface to be used instead of the link-local address that is automatically configured when IPv6 is enabled on the interface. This command enables IPv6 processing on the interface.
    Automatically configure an IPv6 link-local address on the interface, and enable the interface for IPv6 processing. The link-local address can only be used to communicate with nodes on the same link.
    Step 9
    Return to global configuration mode.
    Step 10
    ip routing
    Enable IP routing on the switch.
    Step 11
    ipv6 unicast-routing
    Enable forwarding of IPv6 unicast data packets.

  3. SlimShaddy
    March 23rd, 2017

    No option D for Q 4 will not be correct since the cisco doc reference says “ipv6 enable” is to be used under interface mode while option D talks about enabling on global config mode so read the answers carefully

    April 25th, 2017

    How do you know what kind of class is an ipv6?

  5. SlimShaddy
    April 26th, 2017

    There is no concept of class in IPv6 so the only distinction is based on the various address types as mentioned above under Q2 explanation

  6. Mehr&Ab
    May 15th, 2017

    all EIGRPv3 Routers——–>FF02::A
    all Link Local nodes———>FF02::1
    all OSPFV3 Router———–>FF02::5
    all PIM Routers—————>FF02::D
    all Site-Local Routers——–>FF02::2
    OSPF Designated Routerd—>FF02::6

  7. Muhammad Mohyuddin
    May 16th, 2017


  8. Muhammad Mohyuddin
    May 16th, 2017


    correct answer

  9. Justin
    June 30th, 2017
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