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CCNA > Chapter 24: Implementing IPv6 Addressing on Routers > Flashcards

Chapter 24: Implementing IPv6 Addressing on Routers Flashcards

1
Q

True or False. IPv6 routing is enabled by default on Cisco routers.

A

False. The command ‘ipv6 unicast-routing’ will need to be entered.

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2
Q

What is Modified EUI-64?

A
  • Modified Extended Unique Identifier
  • A way of automatically assigning the second part of a prefixed IPv6 address. (e.g. if you enter FE80::/64 it will work out that the prefix is FE80:0:0:0 and then generate the interface ID using the below method)
    - Split the MAC address of the device/interface in half
    - Insert FFFE in between the two halfs
    - Invert the seventh bit of the interface ID (if it’s a 0 change it to 1 and vice versa)
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3
Q

What do you add to the end of what command to configure an interface with an EUI64 generated address?

A
  • EUI-64 after the address and prefix
  • The full command is ‘ipv6 address <address> <prefix> eui-64</prefix>
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4
Q

True or False. If an interface has a different MAC address configured against it to it’s burned-in address it will use the configured address.

A

True.

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5
Q

If EUI-64 is used to dynamically assign an IPv6 address to an interface that doesn’t have a MAC (e.g. Serial) what will the device use?

A

The MAC of the lowest-numbered interface that does have a MAC.

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6
Q

Which commands allow a router interface to receive an address via DHCPv6 and SLAAC?

A
  • DHCPv6 - ipv6 address DHCP
  • SLAAC - Ipv6 address autoconfig
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7
Q

What are some examples of reserverd IPv6 Multicast addresses?

A
  • FF02::1 - All hosts that use IPv6 on that link (Equivalent to IPv4 224.0.0.1)
  • FF02::2 - All router interfaces that use IPv6 on that link (Equivalent to IPv4 224.0.0.2)
  • FF02::5 - All OSPFv3 routers (Equivalent to IPv4 224.0.0.5)
  • FF02::6 - All OSPFv3 DRs (Equivalent to IPv4 224.0.0.6)
  • FF02::9 - All RIPng routers (Equivalent to IPv4 224.0.0.9)
  • FF02::A - All EIGRPv6 routers (Equivalent to 224.0.0.10)
  • FF02::1:2 - All routers acting as a DHCPv6 relay agent
  • FF02::1:FF/104 - Solicited-node Multicast address
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8
Q

Define the difference between
- Link Local (Unicast) Address
- Link Local Multicast Address
- Link Local (Multicast) Scope

A
  • Link Local Address - An IPv6 address that begins FE80. Serves as an address for an interface to which devices apply a link-local scope (traffic sent here cannot be forwarded by routers)
  • Link Local Multicast Address - An IPv6 address that begins with FF02. Serves as a reserved multicast address to which devices apply a link-local scope
  • Link Local Scope - An IPv6 scope itsself rather than an address. The scope defines the borders within which a packet should and should not be forwarded.
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9
Q

True or False. IPv6 Multicast requires less processing by hosts than IPv4 Multicast.

A

True. This means they can be discarded quicker by hosts that don’t require them.

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10
Q

Why are Solicited Node Multicast Groups necessary?

A

Since ARP is replaced by NDP in IPv6, IPv4 Broadcast ARP is also replaced by IPv6 Multicast. A device attempting to discover a neighbor would know (based on the IPv6 address of the neighbor) the Solicited Node Multicast Group that the neighbor is part of (FF02::1:FF appended with the last 6 hex digits of the neighbor’s address) so it would send an ND message with this as the destination. As the scope is FF02:1 it will be recieved by all nodes on the link but only the device in the Solicited Node Multicast Group will process it.

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10
Q

What is a Solicited Node Multicast address?

A
  • An address associated with a Unicast address that is specifically used for NDP. These will be shown in the below format
    - FF02::1:FF…the last 6 hex digits are also the last 6 digits of the associated unicast address.
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11
Q

What is the “Unkown” IPv6 address?

A
  • A sequence of all 0s or simply ‘::’. This is used when a host doesn’t yet know it’s own IPv6 address. Similar to 169 addresses in IPv4.
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12
Q

True or False. There is an IPv6 equivalent to 127 loopback addresses.

A

True. It is ::1 and acts in the same way.

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13
Q

What is a Solicited Node Multicast address?

A
  • An address associated with a Unicast address that is specifically used for NDP. These will be shown in the below format
    - FF02::1:FF…the last 6 hex digits are also the last 6 digits of the associated unicast address.
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13
Q

What is a Multicast address scope? Provide examples

A
  • An address scope defines a set of rules that dictate whether routers should forward a packet or not (depending on its destination address) and how far that packet is allowed to be forwarded.
  • FF01- Interface Local - Defined by device - Packet remains within the device (e.g. Can be used like a loopback address)
  • FF02 - Link Local - Defined by device - Packet can only be sent on the same link and cannot be forwarded by a router
  • FF05 - Site Local - Configured on router - Intended to be broader than link local but narrower than organization local. Generally limits packets to not being able to cross WAN links
  • FF08 - Organization Local - Configured on router - Intended to be broader than Site Local. Generally for an entire company or organization
  • FF0E - Global - No boundaries
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13
Q

What is an IPv6 Anycast address?

A
  • When a host sends traffic to an Anycast address, the next hop router will forward the traffic to the nearest (based on routing protocol metric) router that has this address configured.
  • Multiple routers can have this same address configured as it generally corresponds to a specific service that is configured on multiple routers.
  • This means that the traffic would not need to be forwarded all the way to a specific router that supports this service.
14
Q

How does a router calculate the Link Local address of an interface where a Global Unicast address is present but the Link Local address has not already been assigned?

A
  • EUI-64 rules are used. Add FFFE into the middle and invert the 7th bit.
15
Q

Why does EUI-64 invert the 7th bit?

A
  • The 7th bit of a MAC address defines whether the MAC address is a UAA or an LAA. It is called the U/L (Universal/Local) Bit.
    - UAA - Universally Administered Address - Assigned by the manufacturer
    - LAA - Locally Administered Address - Assigned by an admin or protocol. Can be input manually on a Cisco interface using
    the mac-address command.
  • If the U/L bit is 1 then the MAC is an LAA. If the U/L bit is 0 then the MAC is a UAA. However in the context of IPv6 this is reversed.
16
Q

What is the command to configure an Anycast address?

A

Just add ‘anycast’ after any IPv6 address you configure on an interface.

17
Q

What is the correct way to display the “Unspecified” IPv6 address and what is it?

A
  • Displayed as ‘::’
  • IPv6 equivalent of 0.0.0.0
  • Can be used when a device doesn’t know its IPv6 address yet
18
Q

What is the IPv6 loopback address?

A
  • Displayed as ‘::1’
  • Same as the IPv4 loopback address
  • IPv6 equivalent to 127.0.0.1

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