IP subnetting!
Arcaneuk
Registered Users Posts: 1 ■□□□□□□□□□
in CCNA & CCENT
Dear all, I have just started the CCENT study guide, and currently going over practice questions at the end of each topic, I do realize that there are number of ways of solving Subnetting problems and I and gradually understanding the concepts.
I have come across a practice question, and I understand the process, but I do not get how they cam to the actual
answers and it is quite frustrating! many I am missing the obvious here, so here goes.
A fellow engineer tells you to configure the DHCP server to lease the last 100 usable IP addresses in subnet 10.1.4.0/23. Which of the following IP addresses could be leased as a result of your new configuration?
Answer: 10.1.5.200
Question #2:
A fellow engineer tells you to configure the DHCP server to lease the first 20 usable IP addresses in subnet 192.168.9.96/27. Which of the following IP addresses could be leased as a result of your new configuration?
Answer: 192.168.9.110
I understand how to find the usable addresses, however i do not get the correct usuable addresses when I calculate it. As an example according to the first answer the last 100 IP address in the range 10.1.4.1 and ending with 10.1.5.254 is between 10.1.5.155 to 10.1.5.254. how do you come to the value 10.1.5.155! and with question #2 how do you get the value according to the answer
" the first 100 IP address in the range 192.168.9.97 and ending with 192.168.9.126 is between 192.168.9.97 to 192.168.9.116"
How do you get the value 192.168.9.116?
I may be doing something silly here, but please help!
Many thanks.
I have come across a practice question, and I understand the process, but I do not get how they cam to the actual
answers and it is quite frustrating! many I am missing the obvious here, so here goes.
A fellow engineer tells you to configure the DHCP server to lease the last 100 usable IP addresses in subnet 10.1.4.0/23. Which of the following IP addresses could be leased as a result of your new configuration?
Answer: 10.1.5.200
Question #2:
A fellow engineer tells you to configure the DHCP server to lease the first 20 usable IP addresses in subnet 192.168.9.96/27. Which of the following IP addresses could be leased as a result of your new configuration?
Answer: 192.168.9.110
I understand how to find the usable addresses, however i do not get the correct usuable addresses when I calculate it. As an example according to the first answer the last 100 IP address in the range 10.1.4.1 and ending with 10.1.5.254 is between 10.1.5.155 to 10.1.5.254. how do you come to the value 10.1.5.155! and with question #2 how do you get the value according to the answer
" the first 100 IP address in the range 192.168.9.97 and ending with 192.168.9.126 is between 192.168.9.97 to 192.168.9.116"
How do you get the value 192.168.9.116?
I may be doing something silly here, but please help!
Many thanks.
Comments
-
rchabrowski
Registered Users Posts: 1 ■□□□□□□□□□
Question 1:
1st usable address: 192.168.9.97
2nd: 192.168.9.98
3rd: 192.168.9.99
...
20th: 192.168.9.116
Question 2:
100th usable address: 10.1.5.254
99th: 10.1.5.253
98th: 10.1.5.252
...
1st: 10.1.5.155
-
rob42
Member Posts: 423
Dear all, I have just started the CCENT study guide, and currently going over practice questions at the end of each topic, I do realize that there are number of ways of solving Subnetting problems and I and gradually understanding the concepts.
I have come across a practice question, and I understand the process, but I do not get how they cam to the actual
answers and it is quite frustrating! many I am missing the obvious here, so here goes.
A fellow engineer tells you to configure the DHCP server to lease the last 100 usable IP addresses in subnet 10.1.4.0/23. Which of the following IP addresses could be leased as a result of your new configuration?
Answer: 10.1.5.200
Question #2:
A fellow engineer tells you to configure the DHCP server to lease the first 20 usable IP addresses in subnet 192.168.9.96/27. Which of the following IP addresses could be leased as a result of your new configuration?
Answer: 192.168.9.110
I understand how to find the usable addresses, however i do not get the correct usable addresses when I calculate it. As an example according to the first answer the last 100 IP address in the range 10.1.4.1 and ending with 10.1.5.254 is between 10.1.5.155 to 10.1.5.254. how do you come to the value 10.1.5.155! and with question #2 how do you get the value according to the answer
" the first 100 IP address in the range 192.168.9.97 and ending with 192.168.9.126 is between 192.168.9.97 to 192.168.9.116"
How do you get the value 192.168.9.116?
I may be doing something silly here, but please help!
Many thanks.
Do you understand 'Blocks' and how to find them?
Do you understand that a /23 has a 'Block Size' of 2, so the Networks are...
0
2
4
6
8
10
etc...
... and the Mask for a /23 Network is 255.255.254.0?
The 'Mask' Boundary is in the 3rd Octet, so that's where the 'Network' Addresses change, so the Networks will be 10.1.0.0, 10.1.2.0, 10.1.4.0, 10.1.6.0. 10.1.8.0, 10.1.10.0 ect...
Network 3 (10.1.4.0) has a usable IP Range of 10.1.4.1 to 10.1.5.254 {10.1.4.0 is the 'Network' and 10.1.5.255 is the 'Broadcast'} and the next Network is 10.1.6.0
So, the 'last 100 usable IP Addresses' for 10.1.4.0 will be (255 - 100 = 155) 10.1.5.155 -> 10.1.5.254
You with me so far?No longer an active member