4 - Packet Delivery

Question 1

What device ampifies and regenerates the signal on its remaining ports?

Answer 1

Hub

Question 2

What is a repeater?

Answer 2

Hub with only two ports

Question 3

How does a switch know that the entire frame arrived safely?

Answer 3

FCS or Frame Check Sequence

Question 4

How does a router check the integrity of an IP Header?

Answer 4

Checksum

Question 5

How does a router check the integrity of the data in a packet?

Answer 5

CRC or cyclic redundancy check

Question 6

What is the default MTU size?

Answer 6

1500 bytes without the header

1518 bytes with the header and crc trailer

Question 7

What is runt?

Answer 7

Frame that is less than 64 bytes and has a bad FCS

Question 8

What is a jumbo frame?

Answer 8

Frame that ranges in size up to 9216 bytes

Question 9

What is the command to change the MTU size?

Answer 9

system mtu xxxx for ethernet and fast ethernet

system mtu jumbo xxxx for gigabit ethernet

Question 10

Whose responsibility is it reassemble fragmented packets?

Answer 10

receiving host

Question 11

What happens to a frame as it passes through a router?

Answer 11

the router strips out the source mac address and replaces it with the outgoing interfaces mac address and the destination mac address will be replaced with the next hops mac address

Question 12

What happens to a packet as it passes through a router?

Answer 12

The router can change the TTL, but most of the IP header is unchanged

Question 13

What is a packet referred to when its a the transport layer or higher?

Answer 13

Flow

Question 14

What is a default gateway?

Answer 14

gateway that is used to communicate with hosts on another network

Question 15

Where does a host operate on the network models?

Answer 15

application layer of the tcp/ip model

session layer and above on the osi model

Question 16

Which device is ultimately the source and destination of packets that traverse the network?

Answer 16

host

Question 17

What is intra-layer communication?

Answer 17

transfer of information between identical tcp/ip layers on different devices

Question 18

What is inter-layer communication?

Answer 18

transfer of information between adjacent tcp/ip layers on the same device

Question 19

What is a PDU that is passed to the next lower layer referred to?

Answer 19

an SDU or service data unit

Question 20

Which layer is referred to as the Host-to-host layer?

Answer 20

Transport layer

Question 21

At what layer of the osi model is a port bound to an application process?

Answer 21

transport layer

Question 22

Describe the TCP three way handshake.

Answer 22

1. Sending host sends a pdu with SYN and sequence number
2. receiving host sends a pdu with SYN and its own sequence number and an ACK with a sequence number one higher of the sending hosts sequence number
3. Sending host sends a pdu with ACK and sequence number one higher of the receiving hosts sequence number

Question 23

What is the port number used for at the transport layer?

Answer 23

used to determine the appropriate application layer process associated with that pdu

Question 24

What does windowing do?

Answer 24

1. improves the speed of tcp communications

2. can improve the reliability by mitigating traffic congestion

Question 25

What does sliding windowing do?

Answer 25

enables tcp to negotiate the window size of a tcp session

Question 26

What happens when a window size is reduced to 0?

Answer 26

the tcp session is dropped

Question 27

Path selection is provided by which layer of the tcp/ip and osi models?

Answer 27

internet layer

network layer

Question 28

What is ARP?

Answer 28

Used to determine the mac address of a particular ip address

Question 29

ARP sends a request to all hosts, what is all hosts at the data link layer?

Answer 29

FF:FF:FF:FF:FF:FF

Question 30

What was reverse arp replaced with?

Answer 30

DHCP because its more robust

Question 31

How do you check arp on windows?

Answer 31

arp -a

Question 32

How do you check arp on a cisco device?

Answer 32

sh ip arp