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Networking > Chapter 7 - IP Addressing > Flashcards

Chapter 7 - IP Addressing Flashcards

1
Q

What is binary?

A

A numbering system that consists of the numbers 0 and 1, called bits.

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2
Q

Why is binary important to understand?

A

Hosts, servers, and network devices use binary addressing to identify each other. Specifically binary IPv4 addresses.

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3
Q

What does an IP address consist of?

A

A string of 32 bits, divided into four section called octets. Each octet contains 8 bits (or one byte) separated with a dot.
I.e.: 11000000.10101000.00001010.00001010.

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4
Q

What makes IPv4 addresses easier to understand?

A

IPv4 addresses are commonly expressed in dotted decimal notation, which is each of the 4 bytes of the address expressed as it’s decimal numbering system equivalent..
i.e.: 192.168.10.10

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5
Q

What is the decimal number 2168 expressed in long form?

A

2 * 1000 (10^3) = 2000
1 * 100 (10^2) = 100
6 * 10 (10^1) = 60
8 * 1 (10^0) = 8

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6
Q

How would you express the decimal number 168 as a binary number?

A 
10101000. 
1 * 128 (2^7) = 128
0 * 64 (2^6) = 0
1 * 32 (2^5) = 32
0 * 16 (2^4) = 0
1 * 8 (2^3) = 8
0 * 4 (2^2) = 0
0 * 2 (2^1) = 0
0 * 1 (2^0) = 0
128 + 32 + 8 = 168
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7
Q

T/F: Some binary digits can be expressed in multiple ways.

A

False, just like decimal, there is only one way to express a binary number.
i.e. 100 is the only way to represent 4 in binary

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8
Q

How would you express the binary number 01101101 as a decimal number?

A 
109
0 * 128 (2^7) = 0
1 * 64 (2^6) = 64
1 * 32 (2^5) = 32
0 * 16 (2^4) = 0
1 * 8 (2^3) = 8
1 * 4 (2^2) = 4
0 * 2 (2^1) = 0
1 * 1 (2^0) = 1
64 + 32 + 8 + 4 + 1 = 109
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9
Q

How would you express the IP address 11000000.10101000.00000001.01100101 in decimal?

A 
192.168.1.105
Divide the IP address into it's 4 octets and then convert each one from binary to a decimal number:
11000000 = 192
10101000 = 168
00000001 = 1
01100101 = 105
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10
Q

What is positional notation?

A

Positional notation means that a digit represents different values depending on the position the digit occupies in a sequence of numbers.
i.e.
1234 in decimal.
4 is in the 0th position, and represents 4 * 10^0
3 is in the 1st position, and represents 3 * 10^1
2 is in the 2nd position, and represents 2 * 10^2
1 is in the 3rd position, and represents 1 * 10^3

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11
Q

What is the radix?

A

The radix is the base number of the numbering system. In decimal the radix is 10. In binary the radix is 2.

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12
Q

How would you express 192.168.10.11 in binary?

A

11000000.10101000.00001010.00001011

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13
Q

What are the portions of an IPv4 address? How is this represented?

A

A network portion and a host portion. Within the 32 bit IP address, a portion of the bits identify the network, and a portion of the bits identify the host.

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14
Q

How are the network bits and host bits different?

A

The network bits must be identical for all devices that reside on the same network. If two hosts have the same bit-pattern in the network portion, those two hosts will reside on the same network.
The host bits must be unique to identify a specific host within a network.

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15
Q

What is the subnet mask? What does a subnet mask of 255.255.255.0 mean?

A

It is the way that hosts know which portion of the 32-bit IPv4 address identifies the network and which identifies the host.

A subnet mask of 255.255.255.0 is equivalent to 11111111.11111111.11111111.00000000. When compared to an IP address, such as 192.168.10.10, or 11000000.10101000.00001010.00001010 the digits of each binary number are compared against each other. The 1s in the subnet mask identify the network portion, while the 0s identify the host portion. This means that 11000000.10101000.00001010 is the network portion and 00001010 is the host portion.

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16
Q

What is the logical AND?

A 
Logical AND is the comparison of two bits that produce results as shown below:
1 AND 1 = 1
1 AND 0 = 0
0 AND 0 = 0
1 AND 0 = 0
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17
Q

How is logical AND used to identify the network address?

A

The IPv4 address is logically ANDed, bit by bit, with the subnet mask. ANDing between the address and the subnet mask yields the network address.

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18
Q

Logical AND 192.168.10.10 and 255.255.255.0. What is the resulting network address?

A

First you have to convert into binary, then bitwise AND each digit.
11000000.10101000.00001010.00001010
11111111.11111111.11111111.00000000
This gives you a result of:
11000000.10101000.00001010.00000000
The resulting network address is 192.168.10.0.

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19
Q

The prefix length?

A

The prefix length is an alternate shorthand method of identifying a subnet mask. It is the number of bits set to 1 in the subnet mask, written in slash notation, which is a “/” followed by the number of bits set to 1.
For example 11111111.11111111.11111111.00000000 is “/24”
11111111.00000000.00000000.00000000 is “/8”

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20
Q

What is the first and last host address?

A

First Host Address: The first available host IP address in a network. The host portion always has all 0s except the last bit, which is a 1. i.e.: 00000001
Last Host Address: The last available host IP address in a network. The host portion always has all 1s except the last bit which is a 0. i.e.: 11111110
The range from the First Host Address to the Last Host Address represents the entire possible range of host addresses in a given network.

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21
Q

What is the broadcast address?

A

A special address that communicates with all hosts in a network. For instance, when a host sends a packet to the network broadcast IPv4 address, all other hosts in the network receive the packet. The broadcast address uses the highest address in the network range, the host portion is all 1s.

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22
Q

What is a static IP address? When are they used?

A

An IP address that does not change. In networks some devices require a fixed IP address, for instances, printers, servers, and networking devices. A host can also be configured with a static IPv4 address, however for large networks it would be time-consuming to enter static addresses on each host.

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23
Q

What is a dynamic IP address? How are they assigned? When are they used?

A

An IP address that can change.
Dynamic IP addresses are often used for PCs, tablets, smartphones, printers, and IP phones. These devices make up the largest population of hosts in most networks. The user population and their devices also change frequently which would make it impractical to statically assign IPv4 addresses for each device.

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24
Q

What is DHCP, and what benefits does it provide?

A

Devices are assigned IPv4 addresses dynamically using the Dynamic Host Configuration Protocol (DHCP). A DHCP server will provide a DHCP client with an IPv4 address, a subnet mask, a default gateway, and other configuration information. DHCP does not permanently assign an address to a host, it is only “leased” for a period of time. If the host is powered down or taken off the network, the address is returned to the pool for reuse. This is especially helpful for mobile users that come and go on a network.

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25
Q

What is the range of unicast host addresses?

A

0.0.0.0 to 223.255.255.255. However there are many addresses in this range reserved for special purposes.

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26
Q

What are the types of broadcasts? What do each do?

A

A directed broadcast is sent to all hosts on a specific network. For example. a host on the 172.16.4.0/24 network sends a packet to 172.16.4.255.
A limited broadcast is sent to 255.255.255.255.
By default, routers do not forward broadcasts.

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27
Q

What is the range of multicast host addresses?

A

224.0.0.0 to 239.255.255.255. The IPv4 multicast addresses 224.0.0.0 to 224.0.0.255 are reserved for multicasting on the local network only. A router recognizes that these packets are addresses to a local network, and will not forward them further.

28
Q

What are multicast clients?

A

Hosts that receive particular multicast data. The multicast clients use services requested by a client program to subscribe to the multicast group.

29
Q

How are multicast groups represented?

A

With a single IPv4 multicast destination address. When an IPv4 host subscribes to a multicast group, the host processes packets addressed to this multicast address, and packets addressed to its uniquely allocated unicast address.

30
Q

What are private IP addresses?

A

They are blocks of addresses that are used by most organizations to assign IPv4 addresses to internal hosts. They are not unique and can be used by an internal network. Private IP addresses are not allowed on the internet, and must be filtered (discarded) by Internet Routers.

31
Q

What are the private address blocks?

A
  1. 0.0.0 to 10.255.255.255
  2. 16.0.0 to 172.31.255.255
  3. 168.0.0 to 192.168.255.255
32
Q

What is NAT?

A

Network Address Translation is used to translate between private IPv4 and public IPv4 addresses. This is usually done on the router that connects the internal network to the ISPs network.

33
Q

How does a home router assign IPv4 addresses, and how does it connect to the ISP network?

A

It usually assigns addresses to wired and wireless hosts from the private address of 192.168.1.0 /24. The home router interface that connects to the internet service provider (ISP) network is assigned a public IPv4 address to use on the internet.

34
Q

What are loopback addresses? What is the loopback address range?

A

More commonly identified as just 127.0.0.1, these are special addresses used by a host to direct traffic to itself. For example it can be used on a host to test if the TCP/IP configuration is operational.
The range is 127.0.0.1 to 127.255.255.254

35
Q

What are link-local addresses? What is the link-local address range?

A

More commonly known as the Automatic Private IP Addressing (APIPA) addresses, they are used by a Windows DHCP client to self-configure in the even that there are no DHCP servers available. Useful in peer-to-peer connections.
The range is 169.254.0.1 to 169.254.255.254.

36
Q

What are TEST-NET Addresses? What is the TEST-NET address range?

A

These addresses are set aside for teaching and learning purposes and can be used in documentation and network examples.
The range is 192.0.2.0 to 192.0.2.255.

37
Q

What is classful addressing? What were the classes?

A

In 1981, Internet IPv4 addresses were assigned using classful addressing. Customers were allocated a network address based on one of three classes, A, B, or C.

38
Q

What were the ranges and purpose of each of the classes?

A 
Class A - 0.0.0.0/8 to 127.0.0.0/8. Designed to support extremely large networks with more than 16 million host addresses. It used a fixed /8 prefix with the first octet to indicate the network address and the remaining 3 octets for host addresses. All class A addresses required the most significant bit of the high-order octet be zero creating a total of 128 possible class A networks.
Class B - 128.0.0.0/16 to 191.255.0.0/16. Designed to support the needs of moderate to large size networks with up to approximately 65000 hosts. It used a fixed /16 prefix with the two high-order octets to indicate the network address and the remaining two octets for host addresses. The most significant two bits of the high-order octet must be 10, creating over 16000 networks.
Class C - 192.0.0.0/24 to 223.255.255.0/24. Designed to support small networks with a maximum of 254 hosts. It used a fixed /24 prefix with the first three octets to indicate the network and the remaining octet for the host addresses. The most significant three bits of the high-order octet must be 110 creating over 2 million possible networks.
There is also a Class D multicast block consisting of 224.0.0.0 to 239.0.0.0 and a Class E experimental address block consisting of 240.0.0.0 – 255.0.0.0.
39
Q

What is the downside to classful addressing?

A

A great deal of addresses were wasted, and they exhausted the availability of IPv4 addresses. Not all organizations’ requirements fit neatly into one of the classes. For example a company that had a network with 260 hosts would need to be given a class B address, with more than 65,000 addresses, wasting 64,740 addresses.

40
Q

What is classless addressing?

A

The current system of addressing, implemented in the late 1990s. The formal name is Classless Inter-Domain Routing (CIDR, pronounced “cider”). In 1993 the IETF created a new set of standards that allowed service providers to allocate IPv4 addresses on any address bit boundary (prefix length) instead of only by a class A, B, or C address. This was to help delay the depletion and eventual exhaustion of IPv4 addresses.

41
Q

Who assigns IP addresses?

A

IPv4 and IPv6 addresses are managed by the Internet Assigned Numbers Authority (IANA).

42
Q

What are RIRs? Who is part of it?

A

The IANA manages and allocates blocks of IP addresses to the Regional Internet Registries (RIRs). RIRs are responsible for allocation IP addresses to ISPs who in turn provide IPv4 address blocks for organizations and smaller ISPs. RIRs can also distribute addresses directly to organizations depending on their policies.
RIRs include:
-ARIN: American Registry for Internet Numbers. Manages and maintains IPv4 and IPv6 addresses for North America.
LACNIC: Regional Latin-American and Caribbean IP Address Registry. Manages and maintains IPv4 and IPv6 addresses for Latin America and some Caribbean Islands.
AfriNIC: African Network Information Centre. Manages and maintains IPv4 and IPv6 addresses for Africa.
Ripe NCC: Réseaux IP Europeans. Manages and maintains IPv4 and IPv6 addresses for Europe, the Middle East, and Central Asia.
APNIC: Asia Pacific Network Information Centre. Manages and maintains IPv4 and IPv6 addresses for the Asia and Pacific regions, including Australia.

43
Q

How large is IPv6?

A

IPv6 has a 128-bit address space, providing 340 undecillion addresses (The number 340, followed by 36 zeroes).

44
Q

Why was there a need for IPv6?

A

IPv4 at 32-bits did not have enough addresses to account for the growing number of network devices. IPv6 also included additional enhancements, including the Internet Control Message Protocol version 6 (ICMPv6), which includes address resolution and address auto-configuration not found in ICMPv4.

45
Q

What is the current state of IPv6 rollout?

A

Currently IPv4 and IPv6 exist simultaneously. A full transition is expected to take years.

46
Q

What are some IPv6 migration techniques and how do each work?

A

Dual Stack - Dual Stack allows IPv4 and IPv6 to coexist on the same network segment. Dual stack devices run both IPv4 and IPv6 protocol stacks simultaneously.
Tunneling - Tunneling is a method of transporting an IPv6 packet over an IPv4 network. The IPv6 packet is encapsulated inside an IPv4 packet, similar to other types of data.
Translation - Network Address Translation 64 (NAT64) allows IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4. An IPv6 packet is translated to an IPv4 packet and vice versa.
Tunneling and translation are only used where needed. The goal should be native IPv6 communications from source to destination.

47
Q

What is the preferred format of writing an IPv6 address?

A

X:X:X:X:X:X:X:X
Where X is a hexadecimal number from 0000 to FFFF. Each X is called a hextet, representing 16 bits or four hexadecimal digits.

48
Q

What is the first rule to help reduce IPv6 addresses?

A

Omit any leading 0s in any 16-bit section or hextet.
01AB can be represented as 1AB
009F can be represented as 9F.
In this rule a hextet consisting of all zeroes can be represented simply by a “0”.

49
Q

What is the second rule to help reduce IPv6 addresses?

A

A double colon (::) can replace any single, contiguous string of one or more 16-bit segments consisting of all 0s. The double colon can only be used once within an address, otherwise there would be more than one possible resulting address.

50
Q

Show the rule one conversion and then the compressed format of the IPv6 address 2001:0000:0DB8:1111:0000:0000:0000:0200

A

Omit Leading Zeroes: 2001:0:DB8:1111:0:0:0:200

Compressed: 2001:0:DB8:1111::200

51
Q

What are the types of IPv6 addresses? How is it different from the types of IPv4 addresses?

A

Unicast - Uniquely identifies an interface on an IPv6-enabled device.
Multicast - Used to send a single IPv6 packet to multiple destinations.
Anycast - Any IPv6 unicast address that can be assigned to multiple devices. A packet sent to an anycast address is routed to the nearest device having that address.
There is no broadcast address, however, there is an IPv6 all-nodes multicast address that essentially gives the same result.

52
Q

How is the portrayal of the subnet mask different between IPv4 and IPv6?

A

IPv4 uses dotted-decimal notation subnet mask or prefix length. For instance an IPv4 address of 192.168.1.10 with dotted decimal subnet mask 255.255.255.0 is equivalent to 192.168.1.10/24.
IPv6 only uses the prefix length to represent the network portion of the address, it does not use dotted-decimal subnet mask notation. In IPv6 the prefix length can range from 0 to 128. A typical IPv6 prefix length is /64, meaning the network portion of the address is 64 bits in length, leaving another 64 bits for the interface ID (host portion) of the address.

53
Q

What are the common types of IPv6 unicast addresses?

A

Global Unicast - Similar to a public IPv4 address. Globally unique, Internet routable addresses. Can be configured statically or assigned dynamically. Not required for every IPv6-enabled network interface.
Link-Local - Used to communicate with other devices on the same local link. The term link refers to a subnet. Confined to a single link. Their uniqueness must only be confirmed on that link because they are not routable beyond the link. In other words, routers will not forward packets with a link-local source or destination address. Strictly required for every IPv6-enabled network interface. The link-local range is from FE80::/10 to FEBF::/10. Typically the link-local address of the router is used as the default gateway for other devices on the link.
Unique Local - Similar to RFC 1918 private IPv4 addresses. Used for local addressing within a site or between a limited number of sites. Should not be routable in the global IPv6 and should not be translated to a global IPv6 address. They have a range of FC00::/7 to FDFF::/7.

54
Q

What is the structure of the IPv6 global unicast address?

A

Currently the IPv6 GUA will start with a the first 3 bits as 001. In other words the first hexadecimal digit will start with a 2 or a 3. This is only 1/8th of the total available IPv6 address space. The total range of the first hextet is 0010 0000 0000 0000 (2000) to 0011 1111 1111 1111 (3FFFF).

55
Q

What are the parts of a global unicast address and what do they do?

A

Global Routing Prefix - The prefix, or network portion of the address that is assigned by the provider, such as an ISP, to a customer or site. Customers can include everyone from enterprise business networks to individual households. /48 global routing prefixes are the most common. For example, the IPv6 address 2001:0DB8:ACAD::/48 has a prefix that indicates that the first 48 bits (3 hextets) (2001:0DB8:ACAD) is the prefix or network portion of the address.
Subnet ID - The size of the subnet ID is dependent on the size of the Global Routing Prefix. This ID is used by organizations to identify subnets within their site. The larger the subnet ID, the more subnets available.
Interface ID - Equivalent to the host portion of an IPv4 address. The term interface is used because a single host may have multiple interfaces, each having one or more IPv6 addresses. In most cases a /64 subnet should be used, leaving a 64-bit interface ID.

56
Q

T/F: The all-0s and all-1s host addresses are reserved and cannot be assigned to a device.

A

False. The all-1s address can be used, since IPv6 does not use broadcast addresses. The all-0s address can also be used, but is reserved as a Subnet-Router anycast address, and should only be assigned to routers.

57
Q

What is the command to issue an IPv6 global unicast address on an interface?

A

“ipv6 address [ipv6-address/prefix-length]” Note there is no space between ipv6-address and prefix-length.

58
Q

What are the ways a device can obtain an IPv6 global unicast address automatically?

A

Stateless Address Autoconfiguration (SLAAC) and

Stateful DHCPv6

59
Q

What is SLAAC?

A

Stateless Address Autoconfiguration is a method that allows a device to obtain its prefix, prefix length, default gateway address, and other information from an IPv6 router without the use of a DHCPv6 server. Devices rely on the local router’s ICMPv6 Router Advertisement (RA) messages to obtain the necessary information.

60
Q

How do you enable a router as an IPv6 router?

A

Use the “ipv6 unicast-routing” global configuration command.

61
Q

What does the ICMPv6 RA message contain?

A

Network Prefix and Prefix Length - Tells the device which network it belongs to
Default Gateway Address - This is an IPv6 link-local address, the source IPv6 address of the RA message.
DNS addresses and domain name – Addresses of DNS servers and a domain name.

62
Q

What are the options for an RA message?

A

Option 1: SLAAC Only - The default option. The RA message suggests that the receiving device use the information in the RA message to create its own IPv6 global unicast address and for all other information. The services of a DHCPv6 server are not required. The prefix portion of the address is received in the RA message.
Option 2: SLAAC and Stateless DHCPv6 - The RA message suggests devices use:
-SLAAC to create its own IPv6 global unicast address.
-The router’s link-local address, the RA’s source IPv6 address for the default gateway address.
-A stateless DHCPv6 server to obtain other information such as a DNS server address and a domain name.
Option 3: Stateful DHCPv6 - A device can automatically receive its addressing information including a global unicast address, prefix length, and the addresses of DNS servers using the services of a stateful DHCPv6 server.
The RA message suggests that devices use:
-The router’s link-local address, the RA’s source IPv6 address for the default gateway address.
-A stateful DHCPv6 address for everything else.
A stateful DHCPv6 address maintains a list of which device receives which IPv6 address.

63
Q

What is EUI-64 process?

A

When the client is using SLAAC, the client must generate its own interface ID. The Interface ID can be created using the EUI-64 process or a randomly generated 64-bit number. The Extended Unique Identifier uses a client’s 48-bit Ethernet MAC address, and inserts another 16 bits in the middle to create a 64-bit interface ID.

64
Q

What are the parts of an EUI-64 interface ID?

A
  • A 24-bit OUI (Organizational unique identifier) from the client mac-address, but the 7th bit (the Universally/Locally (U/L) bit) is reversed. This means if the 7th bit is a 0 it becomes a 1 and vice-versa.
  • The inserted 16-bit value FFFE (in hexadecimal).
  • 24-bit Device Identifier from the client MAC address.
65
Q

What is the EUI-64 address of a device whose MAC address is FC:99:47:75:CE:E0?

A

-FC = 1111 1100, 7th bit reversed = 1111 1110 = FE
-Insert FF:FE between the first 24 bits and the last 24 bits
FE:99:47:FF:FE:75:CE:E0

66
Q

What are the advantages and disadvantages of EUI-64?

A

The MAC address of a device can be used to determine the interface ID of that device. It also allows network to easily track an IPv6 address to an end-device using the unique MAC address. This could be considered a disadvantage, however, due to privacy concerns about packets being traced to the actual physical computer.

Networking (8 decks)

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