IP

Question 1

How large are IPv4 addresses?

Answer 1

32 bits

Question 2

What does IP offer no guarantee of?

Answer 2

Packets reaching their destination
Packets arriving in the correct order
Packets arriving undamaged

Question 3

Why were IPv4 addresses made so small?

Answer 3

No one anticipated a network of more than a billion machines.
Computers at the time worked in 32 bits

Question 4

What is the format of an IPv4 address?

Answer 4

The left most part identifies the network and the right most part identifies the host.

Question 5

What is a class A IPv4 address?

Answer 5

If the first bit of the address is a 0, it is a class A address. The next 7 bits identify the network, this gives 127 class A addresses.

Question 6

What is a class B IPv4 address?

Answer 6

If the first bits of the address is 10, it is a class A address. The next 16 bits identify the network.

Question 7

Why are so many IPv4 addresses wasted?

Answer 7

Nobody needs a class A size network. Most early internet networks allocated a class way too large for them, and more could be requested.

Question 8

What is subnetting?

Answer 8

Large class networks can be broken down internally and treated as many smaller networks. Class B networks can be treated as 256 Class C networks.

Question 9

How large are IPv6 addresses?

Answer 9

128 bits

Question 10

How many bits are reserved for the local network in IPv6?

Answer 10

64

Question 11

What is a netmask?

Answer 11

Denoted as /N after an IP address. You logical-AND the IP address with N 1s to get the network address.

Question 12

What is TTL on an IP packet?

Answer 12

Time To Live
Counter that is decremented every time the packet is processed or when the packet is held onto for more than a second
When it hits zero packet is discarded and an error is generated.
Prevents packets endlessly circulating

Question 13

How big is a MAC address and what is it made up of?

Answer 13

48 bits. 3 bytes for the manufacturer and 3 bytes for the device.

Question 14

What sort of systems need statically assigned IP numbers?

Answer 14

Routers and infrastructure devices that need to be up in the very early stages after a power failure

Question 15

How does Dynamic Host Configuration Protocol work?

Answer 15

Client broadcasts a request for an IP number, including its MAC address or some other identifier (DHCPDISCOVER)
Server(s) reserve an available IP number, and broadcast an offer of it with a lease time (how long IP number is valid for)(DHCPOFFER)
Client chooses from offers, and broadcasts a reply containing chosen IP number (DHCPREQUEST)
Server that offered the IP number finishes reserving it and acknowledges (DHCPACK); other servers see that their offer has been declined and unreserve their offer

Question 16

In DHCP how can a client renew their lease on an IP address?

Answer 16

By sending a request directly to the server they are leasing the IP address from.

Question 17

How does DHCP relaying work?

Answer 17

Relay agent embedded into the network, usually in the router. When relay agent hears a broadcast packets. it sends it on to a specific DHCP server after filling in its own address. Server sends responses back to the relay which broadcasts them over the local network.

Question 18

What is Stateless Address Auto Configuration?

Answer 18

Routers broadcast router advertisement packets
From these, a device can deduce the /64 that identifies the network
They then put their 48 bit MAC address, plus some other stuff, into the address and use it