Dear Sir,
i solved below question but need your assistance for final correct answer.

1. What is the default subnet mask for a Class C IP Address 255.255.160.0
255.255.255.0-----yes
255.255.254.0
255.255.255.192

2. The address 172.16.208.16/20 is a host on which of the following subnets: 172.16.176.0?
255.255.240.0
172.16.192.0?255.255.240.0
172.16.208.0?255.255.240.0---- yes
172.16.224.0?255.255.240.0

3. What does the command "tracert" from a windows machine show?
The route along which packets take to reach a destination.---- yes
The response times of devices along the route.
The subnet mask of the remote network
The port of the application you are troubleshooting

4. When would you use the "tracert" command in a troubleshooting situation?
When I need to find out where my packets are going to reach the destination.
When I need to find out the latency of the route to the destination.---- yes
When I need to find out what the default gateway is.
When I need to find out what port the affected application is using.

5. What is the default gateway?
The address of the main router for all traffic not otherwise specified in the routing
table.----- yes
The address of the main layer 3 device for all traffic not otherwise specified in the
routing table.
The server which holds the information about the internet.
A website which holds the information about the internet.

6. In a routing table, what does the network address 0.0.0.0 mean?
All traffic that doesn?t match another network address.---- yes
All traffic going to the internet.
Traffic going to the 0.0.0.0 network
I don?t know

7. Which of the following commands adds a route in windows?
route add 10.0.10.0 MASK 255.255.255.0 192.168.0.1---- yes
route add NETWORK 10.0.10.0 MASK 255.255.255.0 192.168.0.1
route add 10.0.10.0 MASK 255.255.255.0 GATEWAY 192.168.0.1
route add NETWORK 10.0.10.0 MASK 255.255.255.0 GATEWAY 192.168.0.1

8. What happens if no default gateway is configured on a computer?
The computer has normal internet access.---- yes
The computer can only access the local network.
The computer will not be able to communicate with any other computers.
I don?t know.

9. How do you check if a default gateway is defined on a computer?
ipconfig /all --- yes
route print
netstat ?an
arp ?a

10. What sort of device can a default gateway be?
Layer 2 Switch
Layer 3 Switch
Router--- yes
Hub
************************************************** **************************************
1. What is the difference between TCP and UDP?
TCP is session orientated where as UDP is not --- yes
UDP is session orientated where as TCP is not
TCP is best effort where as UDP is not
I don?t know

2. Why do certain applications prefer UDP over TCP?
UDP offers faster transfer of data important to VoIP and Games
UDP requires less overhead during the transfer of data --- yes
UDP guarantees every packet is delivered to the destination
I don?t know

3. What is the 3rd Layer in the 7 Layer OSI Model
Network -- yes
Data Link
Session
Electrons

4. What port does a web site use by default?
TCP 80 --- yes
UDP 80
TCP 443
TCP 8080

5. At which layer of the 5 Layer TCP/IP Model does ICMP belong to?
Network Layer---yes
Transport Layer
Application Layer
IP Layer

6. What is ICMP used for?
Troubleshooting to identify if a host is online --- yes
To send network error messages between network hosts
To check which port is open on a host
To send email.

7. Why would an organisation block ICMP on their network?
Prevent the structure of their network from being identified
Prevent hacking--- yes
Prevent Denial of Service
Cause headaches for Network Engineers

8. What does "port forwarding" mean?
It transfers the existence of a TCP or UDP port from the host to the network edge
It enables outside hosts to connect to internal hosts on specified ports -- yes
It configures internet access for computers
I don?t know

9. When would you restrict access to TCP port 25?
To prevent the internet sending mail to your mail server.
To prevent unauthorised internal hosts from sending mail out.---yes
To stop access to websites
To stop access to ftp sites

10. What is the difference between an IPv6 Packet and an IPv4 Packet?
IPv6 has a larger header to hold the larger IPv6 address -- yes
IPv4 has a larger header to hold the larger IPv4 address
An IPv6 Packet can contain an IPv4 payload
An IPv4 Packet doesn?t contain a version field

Thanking you advance.