10 - IPv6 Flashcards

1
Q

What was IPv4 ARP replaced with in IPv6?

A

NDP (Neighbor Discovery Protocol)

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2
Q

What is the Prefix / prefix length in IPv6?

A

Number of bits that make up the prefix, which is the equivalent of a SubnetID in IPV4

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3
Q

What is a Global Unicast address similar to from IPv4?

A

Public IPv4 address

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4
Q

What is a Global Routing Prefix?

A

A reserved block of IPv6 addresses that only one company can use

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5
Q

What are the first hex digits for IPv6 Unique Local addresses?

A

FD

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6
Q

What are the first hex digits for IPv6 Multicast addresses?

A

FF

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7
Q

What are the first hex digits for IPv6 Link Local addresses?

A

FE80

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8
Q

What are the three parts to an IPv6 address?

A
  • Global Routing Prefix
  • Subnet
  • Interface ID
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9
Q

How many bits is the Subnet section of an IPv6 address?

A

64 - Prefix Length bits

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10
Q

What are the two components of a Prefix/Subnet ID?

A
  • Global Routing Prefix

- Subnet

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11
Q

What is the formal name for the Subnet ID in IPv6?

A

Prefix ID

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12
Q

What is another name for the IPv6 Subnet ID / Prefix ID?

A

Subnet Router Anycast Address

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13
Q

What is SLAAC?

A

Stateless Address Autoconfiguration

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14
Q

What are Unique Local unicast addresses?

A

Private IPv6 addresses

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15
Q

How many bits is the Global ID in a Unique Local Unicast address?

A

40 bits

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16
Q

What are the three components of the first 64bits of a Unique Local address?

A
  • First 8 bits must be FD
  • 40 bit Global ID
  • 16 bits Subnet
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17
Q

What are the three components of the first 64bits of a Unique Local address?

A
  • First 8 bits must be FD
  • 40 bit Global ID
  • 16 bits Subnet
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18
Q

True/False: You can leave a space between the address and the /prefix length when entering the command on the device

A

False

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19
Q

How do you enable IPv6 routing?

A

ipv6 unicast-routing

interface> ipv6 address …

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20
Q

What is an alternative method to static assignment for an IPv6 interface ID?

A

EUI-64 autoconfiguration

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21
Q

What are the steps EUI-64 autoconfiguration uses to build the interface ID?

A
  1. Split the 6byte MAC address of the interface into two halves
  2. Insert FFFE in the middle
  3. Invert the 7th bit of the resultant interface ID
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22
Q

How would you configure an interface using EUI-64?

A

ipv6 address 2001:DB8:1111:4::/64 eui-64

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23
Q

What command is used to override the burned in MAC address for an interface?

A

mac-address 0201.AA00.0001

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24
Q

True/False: You must only enter the prefix and not the full address when configuring an interface address in eui-64 mode or else the command will fail

A

False. IOS automatically converts the address to the matching prefix

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25
Q

What are two ways Cisco routers support to allow a router interface to dynamically learn an IPv6 address?

A
  • Stateful DHCP

- SLAAC

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26
Q

How do you configure a router interface to use DHCP?

A

ip address dhcp

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27
Q

How do you configure a router interface to use SLAAC?

A

ip address autoconfig

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28
Q

What are IPv6 Link Local addresses used for?

A

Not used for normal packet flows containing application data. They are used for overhead protocols and for routing e.g. next hop IP

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29
Q

True/False: NDP uses link-local addresses

A

True

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30
Q

What command could you use to show the link-local address of a neighboring router?

A

show ipv6 route

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31
Q

True/False: Link-local addresses can represent more than one host

A

False. They are Unicast

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32
Q

True/False: Link-local addresses can be automatically generated

A

True

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33
Q

What is the forwarding scope for link-local addresses?

A

Only the link itself. Routers do not forward packets with link-local destination addresses

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34
Q

What do link local addresses always start with? (Including the 54 bits after the first 10)

A

FE80:0:0:0

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35
Q

What three ways can the second half (interface ID) of the link local address be created?

A
  1. Randomly generated
  2. EUI-64
  3. Manually configured
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36
Q

What command would you use to manually configure a link local address?

A

ipv6 address [address] link-local

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37
Q

What are the valid starting prefixes for link-local addresses?

A

FE8
FE9
FEA
FEB

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38
Q

True/False: If not manually configured IOS automatically calculate the link-local address using EUI-64 rules

A

True

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39
Q

What rules does SLAAC use when calculating the interface ID?

A

EUI-64

40
Q

What does the ipv6 enable command do?

A

Enable IPv6 processing on an interface and adds a link-local address but no other unicast IPv6 addresses

41
Q

What kind of link would you only need a link-local address on?

A

WAN links

42
Q

What is the IPv6 Multicast address for OSPFv3 ‘all OSPF routers’?

A

FF02::5

43
Q

What is the IPv6 Multicast address for OSPFv3 ‘all DR routers’?

A

FF02::6

44
Q

What are the IPv4 and IPv6 Multicast addresses for ‘all nodes’?

A

224.0.0.1 / FF02::1

45
Q

What are the IPv4 and IPv6 Multicast addresses for ‘all router interfaces’?

A

224.0.0.2 / FF02::2

46
Q

What is the Multicast address FF02::A used for?

A

To address all EIGRPv6 routers

47
Q

What does Interface-local scope mean?

A

Packet remains within the device e.g. sending to services running on the same host

48
Q

What does Site-local scope mean?

A

Routers can forward packets in this scope but usually not across WAN links

49
Q

What prefix do Link-local Multicast packets start with?

A

FF02

50
Q

What prefix do Link-local Unicast addresses start with?

A

FE80

51
Q

Why is NDP an improvement over the MAC discovery process (ARP)?

A

By sending IPv6 Multicast packets that can be processed by the correct host but discarded with less processing the other hosts in the subnet

52
Q

What is a Solicited-Node Multicast Address used for?

A

Obtaining the L2 address of a node in NDP

53
Q

What is a Solicited-Node Multicast Address?

A

A special address derived from the last 24 bits (6 hex digits) of each Unicast address on an interface

54
Q

What is the format of a Solicited-Node Multicast Address?

A

FF02::1:FF–:—- where the last 6 characters are the last 24 bits of the original Unicast address

55
Q

What special IPv6 address represents unknown (unspecified) address?

A

:: or all 0s

56
Q

What is the loopback IPv6 address?

A

::1

57
Q

What is an IPv6 Anycast address?

A

An address that can be configured on a number of router interfaces and causes a packet to be delivered to the closest one

58
Q

What prefix are Anycast address routes advertised as?

A

128 bits (as a host route)

59
Q

How do you configure an IPv6 Anycast address on a router interface?

A

ipv6 address 2001:1:2:99/128 anycast

60
Q

What is the Subnet Router Anycast address?

A

One special Anycast address in each subnet, reserved by routers as a way to send a packet to any router on the subnet. Effectively the network address of that subnet (all 0s in host)

61
Q

What is the value of the Subnet Router Anycast address?

A

Same prefix/number as the SubnetID address, all 0s on the interface ID

62
Q

True/False: Routers add connected or local IPv6 routes for link-local addresses

A

False

63
Q

What two routes will routers make for each Unicast IPv6 address on an interface (excluding link-local addresses)?

A
  • A connected route for the subnet

- A host route for the interface address

64
Q

What command would you use to show all Local IPv6 routes?

A

show ipv6 route local

65
Q

What command would you use to show all Connected IPv6 routes?

A

show ipv6 route connected

66
Q

How would you configure a static IPv6 route by specifying an outgoing interface?

A

ipv6 route 2001:DB8:1111:2::/64 s0/0/0

67
Q

How do you show a particular route to a specified destination?

A

show ipv6 route [ip]

68
Q

Why must you specify both an outgoing interface and link-local address when using a link-local address as the next-hop for a static IPv6 route?

A

Because the link-local address by itself does not tell the local router which outgoing interface to use

69
Q

How would you configure a static route using a link-local next-hop address?

A

ipv6 route [dest] [outgoing interface] [link-local next-hop]

70
Q

What must you always do when configuring a static route that uses an Ethernet interface?

A

Include a next-hop IP address. You cannot only specify an outgoing interface

71
Q

What is the IPv6 default route?

A

::/0

72
Q

How would you make a floating static route?

A

ipv6 route [destination] [next-hop] [metric]

73
Q

What is a floating static route?

A

A static route with a custom administrative distance value that floats in / out of the routing table depending what better (lower) routes exist with lower administrative distance

74
Q

What is the default administrative distance for connected routes?

A

0

75
Q

What is the default administrative distance for NDP learned routes?

A

2

76
Q

What is the default administrative distance for OSPF routes?

A

110

77
Q

What is the default administrative distance for RIP routes?

A

120

78
Q

When using SLAAC how does the host learn the subnet (prefix) and prefix length used on the link ?

A

NDP

79
Q

What is DAD and how do hosts perform it?

A

Duplicate address detection.

Hosts use NDP to ensure no other hosts uses the same IPv6 address before attempting to use it

80
Q

True/False: NDP is part of ICMPv6

A

True

81
Q

What replaces ARP Request and Reply messages in NDP?

A

Neighbor Solicitations and Neighbor Advertisements

82
Q

What does a Neighbor Solicitation (NS) message do?

A

Asks the host with a particular IPv6 address to reply with an NA that lists its MAC

83
Q

What is the destination address of a NS message?

A

Solicited Node Multicast address associated with the target address.

Therefore the message is only processed by hosts whose last six hex digits match the address being queried

84
Q

What does a Neighbor Advertisement (NA) message do?

A

Lists the senders IPv6 and MAC.

Sent in reply to an NS or can be sent as an unsolicited NA, announcing its addresses to all IPv6 hosts

85
Q

What is the destination address of an unsolicited Neighbor Advertisement?

A

FF02::1

This is the ‘all IPv6 hosts’ local-scope multicast address

86
Q

What is the NDP neighbor table?

A

The equivalent of the IPv4 ARP cache

87
Q

What is the multicast address for all IPv6 hosts local scope?

A

FF02::1

88
Q

How can hosts learn the identity of a default gateway differently in IPv6?

A

Using NDP with RS and RA messages

89
Q

What is a Router Solicitation (RS) message?

A

A message sent to all IPv6 routers on the local link to ask for their details

90
Q

What is the destination address of a Router Solicitation message?

A

FF02::2

This is the ‘all IPv6 routers’ local-scope multicast address

91
Q

What is a Router Advertisement (RA) message?

A

Lists facts about the router, either in response to an RS or by itself e.g. link-local address

92
Q

True/False: An RA does not list more than one prefix or default routers to be listed

A

False. IPv6 allows multiple prefixes and multiple default routers to be listed in RA messages

93
Q

True/False: IPv6 does not use Broadcasts

A

True. It uses Multicast instead

94
Q

What alternative to DHCP does IPv6 support for dynamic address assignment?

A

SLAAC

95
Q

What are the three steps involved in SLAAC?

A
  1. Learn the IPv6 prefix used on the link from any router using NDP RS/RA
  2. Build an address from the prefix + interface ID, using a random value or EUI-64 rules
  3. Use DAD before using the address
96
Q

When do hosts use DAD?

A

Anytime the interface initializes

  • End of SLAAC
  • Static address configuration
  • DHCP
97
Q

What are the initial 104bits of a Solicited Node Multicast Address?

A

FF02::1:FF