slides17

Question 1

Dynamic Host Configuration Protocol

Answer 1

When a machine needs an IP address it can use DHCP to get one

Question 2

how is DHCP initated

Answer 2

When a host boots and finds it needs an IP address, it makes a DHCP broadcast

Question 3

difference ARP and DHCP

Answer 3

In contrast to ARP, with DHCP there is usually just one or occasionally more hosts that are configured to respond to DHCP requests, as allocation of addresses must be centrally managed to avoid duplication

Question 4

DHCP additional

Answer 4

DHCPDECLINE client says no DHCPNAK server says no

Question 5

lease time

Answer 5

The address is usable by the requesting host for this period of
time
If the lease expires the host can request a renewal of the lease from the server

Question 6

Internet Control Message Protocol

Answer 6

error packet

Question 7

ICMP Type

Answer 7

kind of message, e.g., “TTL expired”, “destination unreachable”, “fragmentation needed but DF set”

Question 8

ICMP

Answer 8

additional information, e.g., “destination unreachable” has “network unreachable” and “host unreachable” codes

Question 9

ICMP response error message

Answer 9

This message (in an IP packet) will have IP source address of the router; and destination address the source of the problem packet

Question 10

ICMP errors are not generated for

Answer 10

• ICMP errors (e.g., TTL expires on a ICMP packet)
• a packet whose destination is a broadcast or multicast • a packet whose source is a broadcast or multicast
• a packet whose link-layer address is a broadcast
• any fragment other than the first

Question 11

how to discover if a machine is up and running

Answer 11

ICMP ping

Question 12

max addresses recorded by ping and why

Answer 12

there can only be 60 bytes of options in IPv4, giving space for up to 9 addresses (with the overheads of the option header and other bits and pieces), so only 9 addresses are recorded