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CCNA > Chapter 22 - Fundamentals of IPv6 > Flashcards

Chapter 22 - Fundamentals of IPv6 Flashcards

1
Q

How many bits is an IPv6 address comprised of?

A

128-bits

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2
Q

What protocols are receiving “Upgrades” in the transition from IPv4 to IPv6?

A
  • OSPF is moving from V2 to V3 as V2 does not support IPv6 routing. V3, however, supports both IPv6 and IPv4 routing.
  • ICMP is moving to ICMPv6 as the current version of ICMP does not support IPv6.
  • ARP is moving to Neighbor Discovery Protocol.
  • RIP is moving to RIPng (Next Generation) as RIP does not support IPv6 routing.
  • EIGRP is moving to EIGRPv6 as EIGRP does not support IPv6 routing.
  • BGP is moving to MP BGP-4 (Multiprotocol BGP version 4) as BGP-4 does not support IPv6 routing.
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3
Q

True or False. IPv6 uses hexadecimal.

A

True. It is comprised of 32 hexadecimal digits.

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4
Q

What basic concepts does IPv6 use similarly to IPv4?

A
  • To be able to send an IPv6 packet out of an interface, that interface must have an IPv6 address.
  • Hosts with IPv6 addresses need to know the IPv6 address of their default gateway.
  • IPv6 routers deencapsulate and reencapsulate each IPv6 packet when routing.
  • IPv6 routers make routing decisions based on a packets dst IPv6 address when compared to its routing table.
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5
Q

What is the configuration called when IPv4 and IPv6 work alongside each other?

A

Dual stack.

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6
Q

What are the three main things to remember about abbreviating IPv6 addresses?

A
  • In each quartet (set of 4 hex characters), remove all 0s to the left. In a quartet with 4 0s this is abbreviated as a single 0.
  • Replace any string of two or more quartets of all 0s with “::”. If there are multiple of these then replace the longest string (e.g. a string of 16 0s would be replaced with “::” over a string of 8 0s) This can only be used once in a single IPv6 address.
  • Never remove 0s to the right of a quartet.
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7
Q

What is the range of prefix lengths for IPv6 prefixes?

A

0 to 128

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8
Q

How many bits is a single IPv6 character?

A

4 bits

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9
Q

How do you find the subnet ID of an IPv6 address?

A

If prefix was P then just copy P bits from the IPv6 address and change the rest to 0.

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10
Q

How do you find the subnet ID of an IPv6 address if the prefix is a multiple of 4?

A
  • Divide the prefix length by 4 and make that answer E
  • Copy E hex digits
  • Change the rest to 0
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11
Q

How do you find the Global Routing Prefix of an IPv6 address with odd Prefix bits?

A

The method I use is to count upto the prefix bit (in the first example the 65th) and put it into binary (6 - 0110). The first bit of the hex digit 6 is the 65th so any bit after that is free reign, hence why it is upto 7 as that’s the sum of leftover bits.
For example:

9812:F43E:7834:E901:6391:0042:/65

The global routing prefix of this one is

9812:F43E:7834:E901:: upto 9812:F43E:7834:E901:7FFF…….

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12
Q

True or False. Broadcasts can be sent in IPv6 networks.

A

False. There is no longer broadcast, only multicast that achieves the same goal. For example, sending something to all devices in a broadcast domain in IPv4 would be the IPv6 equivalent of sending something to the local scope multicast address (FF02::1).

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13
Q

What are four of the main functions of NDP?

A
  • Neighbor MAC Discovery - Just like IPv4, hosts need to learn each other’s MAC addresses to send frames. This is done by NDP rather than ARP, and messages replace the ARP Request and Reply
  • Router Discovery - Hosts learn the IPv6 addresses of the available IPv6 routers in the same subnet
  • SLAAC - When using SLAAC, a host will use NDP to learn the subnet and prefix length used on its local link
  • DAD (Duplicate Address Detection) - Before configuring an IPv6 address, or enabling an IPv6 capable interface, hosts will use the DAD process to ensure no hosts use the same IPv6 address.
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14
Q

What is the IPv6 equivalent of the ARP Request?

A
  • Neighbor Solicitation (NS) - Asks a host to reply with its MAC address. This is sent to the solicited node multicast group of the required host so only they will process it.
  • ICMPv6 type 135
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15
Q

What is the IPv6 equivalent of the ARP Reply?

A
  • Neighbor Advertisement (NA) - A response to an NS containing the sending host’s MAC address. This is sent to the IPv6 address of the sender of the NS, however, unsolicited NAs can also be sent to all IPv6 hosts in the same broadcast domain (local scope multicast address) (FF02::1).
  • ICMPv6 Type 136
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16
Q

What is the IPv6 equivalent of an ARP cache?

A

NDP Neighbor Table

17
Q

True or False. IPv6 devices learn of their default gateway in the same way that IPv4 devices do.

A

False. IPv4 devices are told their default gateway either statically or using a dynamic method (e.g. DHCP). IPv6 devices learn about possible default gateways using RS (Router Solicitation) and RA (Router Advertisement)

18
Q

What is Router Solicitation (RS)?

A
  • This message is sent to the all IPv6 routers local scope multicast address (FF02::2) so that only IPv6 routers on the local link (not other devices) will identify themselves. This reduces load on host devices as they don’t need to process messages sent to FF02::2.
  • ICMPv6 Type 133
19
Q

What is Router Advertisement (RA)?

A
  • This message is sent by an IPv6 router in response to an RS message. They can also be sent without being asked, these are sent periodically to FF02:1 (all IPv6 devices on the link). It lists information about the sending router including the link-local IPv6 address of the router. When sent in response to an RS message it can either be sent back to the unicast address of the requester or to FF02::1.
  • ICMPv6 Type 234
20
Q

How does SLAAC use NDP to apply addresses?

A
  • The host learns the subnet used on a particular link from a router using RS/RA messages
  • Build an address from the prefix of the subnet plus the interface ID (EUI-64 or a statically assigned random value)
  • Use the DAD process to make sure no other host is already using the same address
21
Q

True or False. DAD is used only when SLAAC is being utilised for address delegation.

A

False. DHCP, SLAAC, and even statically assigned addresses will be subject to this process.

22
Q

What happens if two devices attempt to use the same address?

A

The second device attempting to use this address will simply not use this address and will be assigned another one.

23
Q

How does a device use the DAD process to find out if there is a duplicate address?

A

A device will send an NS for its own IPv6 solicited node multicast address. Since this is the device’s own address, no other device should respond. If something does respond with an NA then the device knows that there is a duplicate address.

24
Q

When does a host device use the DAD process?

A

Whenever an address or device has an address configured (even a link-local address) and whenever the host’s interface comes up.

25
Q

How big is the IPv6 header?

A
  • 40 bytes. It is fixed at this lenght
26
Q

List and describe the different parts of the IPv6 header?

A
  • Version - Defines the IP version (6 in an IPv6 header) - 4 bits
  • Traffic Class - Used for QoS to indicate high priority traffic (e.g. real time traffic will have a higher priority over other traffic) - 8 bits
  • Flow Label - Used to identify specific traffic flows (traffic from specific sources to specific destinations) - 20 bits
  • Payload Length - Defines the length of the layer 4 segment payload in bytes. - 16 bits
  • Next Header - Defines the type of the next header. This will be the header of the encapsulated segment (e.g. TCP). Same as the IPv4 protocol field. - 8 bits
  • Hop Limit - Decrements by 1 for each router that forwards the packet. If this reaches 0 then the packet is discarded. - 8 bits
  • Source and Destination Address - Defines the source and destination address of the packet. - 128 bits each
27
Q

What command is used to configure an address on an interface using SLAAC?

A

ipv6 address autoconfig

28
Q

True or False. IPv6 routing can function on a router without the ‘ipv6 unicast-routing’ command having been configured.

A

False. Although, the router can still forward IPv6 packets, just not between networks (routing).

29
Q

How to convert Decimal to Hexadecimal

A
  • Tip: Only the remainder matters
  • Divide decimal number by 16.
  • Times remainder by 16. If there was no remainder move to next step
  • Divide whole number of prior to last calculation by 16.
  • Times remainder by 16. If there was no remainder move to next step
  • Repeat the above until you reach a number that when divided by 16 goes below 0
  • Times the result by 16
  • The answer is the number from bottom to top

Example:
- 605/16 = 37.8125
- 0.812516 = 13 (D - Last number in answer)
- 37/16 = 2.3125
- 0.312516 = 5 (Middle number in answer)
- 2/16 = 0.125
- 0.125*16 = 2 (First number in answer)

30
Q

How to convert Hexadecimal to Decimal

A
  • Similar to binary, each character position is worth a different amount. In binary it goes 1, 2, 4, 8, 16, 32 etc.
    -In Hex it is 1, 16, 256, 4096, 65536 etc.
  • Set the characters out as:

65536 4096 256 16 1
0 0 D 3 2

  • In this example it would be:
    065536
    0    4096
    13256 = 3328
    3    16 = 48
    2*1 = 2

3328 + 48 + 2 = 3378

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