Broadcast and Rang of Addresses in a Subnet
What is the range of usable IP’s:
Subnet number (smallest number)-cannot be assign to a host
Broadcast number (largest number)-cannot be assign to a host
Usable IP’s are the numbers between Subnet number and Broadcast number.
Subnet number is 129.100.96.0, mask 255.255.224.0 (/19)
First usable address: 129.100.96.1
Last usable address: 129.100.96.254
Subnet Broadcast is 129.100.96.255
Finding Broadcast and Rang of Addresses in a Subnet 1
129.96.100.89/19
255.255.224.0
SPECIAL= 32
First 6 steps are the same as in Finding the subnet section
7. For Broadcast octet to the left of the rectangle, where Subnet mask is 255 copy subnet number
8. For Broadcast octet to the right of the rectangle, where Subnet mask is 0, type 255.
9. For Broadcast number in interesting octet:
Subnet’s interesting octet is 96, SPECIAL is 32.
96+32-1= 127 (Broadcast values in interesting octet)
10. First IP:
Copy first three octets from Subnet number to the first three octet in First IP row.
4th octet of First IP row: Subnet number value from 4th octet +1, so is 0+1=1
11. Last IP:
Copy first three octets from Broadcast. 4th octet of Last IP row: Broadcast value from 4th octet -1, so it's 255-1=254
Finding Broadcast and Rang of Addresses in a Subnet 2
192.168.2.148/19
255.255.255.240
First 6 steps are the same as in Finding the subnet section
SPECIAL=256-240
SPECIAL= 16
7. For Broadcast octet to the left of the rectangle, where Subnet mask is 255 copy subnet number
8. For Broadcast octet to the right ----NONE
In this situation we calculate:
Subnet interesting octet = 144, SPECIAL = 16
Our formula will be: 144+16-1 =159
9. First IP:
Copy first three octets from Subnet number. Into the 4th octet type Subnet number from 4th octet +1, so is 144+1= 145
11. Copy first three octets from Broadcast. Into the 4th octet type Broadcast value from 4th octet -1, so is 159-1= 158
Source:CCENT/CCNA ICND1 Official Exam Certification Guide, Second Edition [Wendell Odom]