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Indicate whether the statement is true or false.
1. Routers send ICMP Redirect messages to hosts to indicate that a preferable route exists.
a.
True
b.
False
2. ICMP packets contain only three required fields after the IP header: Type, Code, and Checksum.
a.
True
b.
False
3. Routers can use ICMP to provide a default gateway setting to a host (if the host requests assistance).
a.
True
b.
False
4. The value 0 in the IP header Protocol field denotes that an ICMP header follows the IP header.
a.
True
b.
False
5. With router advertising, the default Lifetime value for route entries is 10 minutes.
a.
True
b.
False
Indicate the answer choice that best completes the statement or answers the question.
6. Which of the following ICMP packet fields provide error detection for the ICMP header only?
a.
Checksum
b.
Type
c.
Host
d.
Code
7. Which of the following enables a source to learn the currently supported MTU across an entire path, without
requiring fragmentation?
a.
Firewalking
b.
Traceroute
c.
Pathping
d.
PMTU Discovery
8. Of which of the following ICMP replies are there two versions, which are: the standard version that simply
states the packet had the Don’t Fragment bit set when it reached a router that needed to fragment it, and the
PMTU version that includes information about the restricting link?
a.
Code 2: Protocol Unreachable
b.
Code 3: Port Unreachable
c.
Code 4: Fragmentation Needed and Don’t Fragment Was Set
d.
Code 5: Source Route Failed
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9. A host or router can send which of the following error message to indicate that the protocol defined in the IP
header cannot be processed?
a.
Code 2: Protocol Unreachable
b.
Code 3:Port Unreachable
c.
Code 4: Fragmentation Needed and Don’t Fragment Was Set
d.
Code 5: Source Route Failed
10. Which of the following may a router or host use as a way to indicate that it is becoming congested or
overloaded?
a.
Checksum
b.
Source Quench
c.
GMT
d.
PMTU
11. Which of the following can hackers can use as part of a reconnaissance process to learn about active
network addresses and active processes?
a.
availability
b.
ICMP
c.
auto recovery
d.
presence
12. What protocol protects the authentication and confidentiality of ICMPv6 exchanges?
a.
IPsec
b.
WPA2
c.
PPTP
d.
SHA-2
13. Which ICMP reply does a router send in order to indicate that the router cannot use the strict or loose source
routing path specified in the original packet?
a.
Code 2: Protocol Unreachable
b.
Code 3: Port Unreachable
c.
Code 4: Fragmentation Needed and Don’t Fragment Was Set
d.
Code 5: Source Route Failed
14. Which of the following message types document when routing or delivery errors prevent IP datagrams from
reaching their destinations?
a.
ICMP Echo/Echo Reply
b.
ICMP Source Quench
c.
ICMP Time Exceeded
d.
ICMP Destination Unreachable
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15. Which of the following is a command-line utility that uses ICMP Echo packets to test router and link
latency, as well as packet loss?
a.
NTP
b.
Pathping
c.
Path MTU
d.
Traceroute
16. Which of the following utilities use route tracing to identify a path from the sender to the target host?
a.
gateway
b.
Traceroute
c.
firewalking
d.
auto-recovery
17. Which of the following message types permit a gateway (router) on a nonoptimal route between sender and
receiver to redirect traffic to a more optimal path?
a.
ICMP Echo/Echo Reply
b.
ICMP Source Quench
c.
ICMP Redirect
d.
ICMP Destination Unreachable
18. Which of the following types of messages serves to keep hosts apprised of networking conditions and
problems, and equipped to use best paths around the network?
a.
NTP messages
b.
Path MTU messages
c.
ICMP messages
d.
GMT messages
19. If configured to do so, routers periodically send unsolicited ICMP Router Advertisements to which of the
following all-hosts multicast address?
a.
224.0.0.1
b.
255.255.0.0
c.
224.255.0.1
d.
255.224.0.1
20. Which RFC defines a method for discovering a Path MTU (PMTU) using ICMP?
a.
RFC 1191
b.
RFC 1241
c.
RFC 1542
d.
RFC 1577
21. Which message type supports functionality for reachability utilities like Ping and Tracert; essential when
installing, configuring, and troubleshooting IP networks?
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a.
ICMP Echo/Echo Reply
b.
ICMP Source Quench
c.
ICMP Time Exceeded
d.
ICMP Destination Unreachable
22. Which of the following typically learn about routes through manual configuration of the default gateway
parameter and redirection messages?
a.
Packets
b.
Firewalls
c.
Ports
d.
IP hosts
23. For any network node to communicate and exchange data with another network node, some way of
forwarding packets from the sender to receiver must exist. What is this concept called?
a.
response time
b.
route tracing
c.
reachability
d.
network congestion
24. Using which of the following as well as some manipulation of the TTL value in the IP header, Traceroute
results provide a list of routers along a path, as well as the round-trip latency time to each router?
a.
ICMP Echo Requests
b.
ICMP paths
c.
ICMP metrics
d.
ICMP query messages
25. Which of the following processes is one method of obtaining a list of the active hosts on a network?
a.
ICMP query
b.
query
c.
IP address scanning
d.
firewalking
26. Which of the following ICMP Types is used for Echo Request packets?
a.
ICMP Type 2
b.
ICMP Type 4
c.
ICMP Type 6
d.
ICMP Type 8
Enter the appropriate word(s) to complete the statement.
27. An IP ____________________ is performed by sending a ping packet (ICMP Echo Request packet) to each
host within a range and noting the responses.
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28. The PMTU specification defined in RFC 1191 requires the PMTU host to try periodically a larger MTU to
see if the ____________________ has increased.
29. ICMP Type ____________________ is used for Echo Reply packets.
30. Two of the most well-known utilities, Ping and Traceroute, rely on ICMP to perform connectivity tests and
____________________.
31. ____________________ describes the concept of walking a firewall ACL or ruleset to determine what it
filters, and how.
Match each item with a statement below.
a.
Network congestion
b.
firewalking
c.
ICMP query message
d.
inverse mapping
e.
ICMP Echo communication
f.
overhead
g.
reachability
h.
throughput difference
i.
restricting link
32. a condition that occurs when the delivery time for packets increases beyond normal limits
33. a two-staged reconnaissance method involving an initial perimeter device discovery phase and subsequent
inverse mapping of filtered devices
34. an ICMP message that contains requests for configuration or other information
35. the process of identifying live network hosts positioned behind a filtering device by probing for addresses
known not to be in use
36. an ICMP process whereby a host sends an Echo packet to another host on an internetwork
37. the non-data bits or bytes required to move data from one location to another
38. the ability to find at least one transmission path between a pair of hosts so they can exchange datagrams
across an internetwork
39. the comparative difference in throughput between two paths and is measured in Kbps or Mbps
40. a link that does not support forwarding based on the current packet format and configuration
41. What is the purpose of the following ICMP message types: ICMP Redirect, ICMP Time Exceeded, and
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ICMP Parameter Problem?
42. Describe the ICMP message Code 3 Port Unreachable.
43. What is firewalking?
44. Briefly describe an ICMP redirect attack.
45. According to RFC 792, what is the relationship between IP and ICMP?
46. Briefly describe the fields that are included in the ICMPv4 Router Advertisement packets (after the ICMP
Checksum field).
47. Briefly describe an ICMP router discovery attack.
48. Briefly define the following codes, currently assigned to the ICMP Destination Unreachable type number:
Code 2: Protocol Unreachable, Code 3:Port Unreachable, and Code 5: Source Route Failed.
49. Describe some of the security issues for ICMPv6.
50. How does inverse mapping determine live targets on a network?
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Router Address 2 and Precedence Level 2: If there are additional router values, they will follow with their precedence
levels.
indicating that his machine is actually the immediate router in question, and not the actual router on the network segment.
source routing path specified in the original packet.
mechanism is currently specified that would prevent an attacker on the local network from exploiting ICMPv6 to
ICMPv6 is protected by IPsec, but this presents a security bootstrap problem because IPsec is not available when a
computer is at this state.
network addresses, it will promptly reply with a Host Unreachable message for every bogus entry requested. The attacker
ICMP messages take the form of specially formatted IP datagrams, with specific associated message types and codes.
ICMP is a required element in some implementations of TCP/IP, most notably those TCP/IP protocol stacks judged
suitable for sale to the U.S. government, and ICMP is usually present to provide an essential part of IP’s support fabric.
ICMP reports errors only about processing of non–ICMP IP datagrams. To prevent an endless loop of messages about
error messages, ICMP conveys no messages about itself and provides information only about the first fragment in any
sequence of fragmented datagrams.