# Need Help w/ Networking Exam Questions Please!



## Ross211 (Apr 17, 2010)

I am thinking there are some experts in here that can answer some questions that I have on my practice exam for my networking class.  Don't laugh too hard, these questions aren't very in depth, but I can't seem to understand - and my exam is this Monday.  I've tried reading my textbook but I'm not certain on my answers after doing the work.

Anyways, here they are -

*1.	 In the IP address, 10.11.13.13, what is the network part?*
The IP 10.11.13.13 is a private IP address.  Also, there is no way to tell by looking at an IP address what sizes the network, subnet, and host parts are- only their total of 32 bits.  We can’t determine the network part without a mask.

*2.	In the IP address, 198.165.50.15/18, what is the network part?*
/18 = mask of 255.255.192.0
1100 0110	1010 0101	0011 0010	0000 1111 (IP Address - 198.165.50.15)
1111 1111 	1111 1111 	1100 0000	0000 0000 (Mask)
1100 0110	1010 0101	0000 0000	0000 0000 (Result after applying mask)

*198.165 is the network part - (Is this right???)
*

*3.	Mask 188.156.149.15 and 255.255.140.0.*
1011 1100	1001 1100	1001 0101	0000 1111 (IP  Address - 188.156.149.15)
1111 1111	1111 1111	1000 1100	0000 0000 (Mask)
1011 1100	1001 1100	1000 0100	0000 0000 (Result after applying mask)

*188.156.132.0 - (Is this right???)
*

*4.	In the IP address, 155.162.58.13/18, how many bits are in the host part?*
1001 1011	1010 0010	0011 1010	0000 1101 (IP address)
1111 1111	1111 1111	1100 0000	0000 0000 (Mask)
1001 1011	1010 0010	0000 0000	0000 0000 (Result after applying mask)

*
155.162.0.0
16 bits are in the host part (Is this right???)*
^____^ - Can you cheat and use the IP address classes to determine how many bits are the host part?

	Class A – first octet value 1-127
		Can have as many as 16 million hosts
	Class B – first octet value 128-191
		Can have as many as 65000 hosts – 16 bits local part
	Class C – first octet value 192-223
		254 possible hosts – 8 bits local part
	Class D – first octet value 224-239
		Used for multicasting

Since the IP is 155.162.58.13 - it would make it a class B IP address.  I'm assuming that 155.162.58.13/18 has a 16 bit host part.  So, since the host part is 16 bits, this gives 2^16 = 65536 possibilities. (~6500 hosts)

How do you tell if a mask is a subnet mask or a network mask?

Can you tell just by the /18 in 198.165.50.15/18 for example?

I will probably post back with a few more questions when I have them.

Thank you and god bless whoever helps me!


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## Oliver_FF (Apr 18, 2010)

Ross211 said:


> *1.	 In the IP address, 10.11.13.13, what is the network part?*
> The IP 10.11.13.13 is a private IP address.  Also, there is no way to tell by looking at an IP address what sizes the network, subnet, and host parts are- only their total of 32 bits.  We can’t determine the network part without a mask.



An IP address who's first digit is between 1 and 127 is a class A address, so the network is denoted by bits 31-24 inclusive (don't forget bits are counted right to left) so it is '10'.




Ross211 said:


> *2.	In the IP address, 198.165.50.15/18, what is the network part?*
> /18 = mask of 255.255.192.0
> 1100 0110	1010 0101	0011 0010	0000 1111 (IP Address - 198.165.50.15)
> 1111 1111 	1111 1111 	1100 0000	0000 0000 (Mask)
> ...



I agree.





Ross211 said:


> *3.	Mask 188.156.149.15 and 255.255.140.0.*
> 1011 1100	1001 1100	1001 0101	0000 1111 (IP  Address - 188.156.149.15)
> 1111 1111	1111 1111	1000 1100	0000 0000 (Mask)
> 1011 1100	1001 1100	1000 0100	0000 0000 (Result after applying mask)
> ...



I agree.





Ross211 said:


> *4.	In the IP address, 155.162.58.13/18, how many bits are in the host part?*
> 1001 1011	1010 0010	0011 1010	0000 1101 (IP address)
> 1111 1111	1111 1111	1100 0000	0000 0000 (Mask)
> 1001 1011	1010 0010	0000 0000	0000 0000 (Result after applying mask)
> ...



For "155.162.58.13/18" the "/18" shows that the network mask is 18 bits long. All IP addresses are 32 bits long, so the number of bits in the host is 32-18 = 14


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