内功心法
1.几种逻辑运算
AND OR NOT
a AND 0and 0=0 1and1=1 0and1=0
b OR 0OR0=0 1OR1=1 0OR1=1
C NOT NOT0=1 NOT1=0
EXAMPLE:
给一IP地址：139.175.152.254/16
NET ID不用解释
HOST ID:先将NET MASK 做一个NOT运算，在和IP做一次AND就得出HOST ID
Broadcast ID;先将NET MASK作一个NOT 运算，在和IP做一次OR运算得出
Broadcast ID
2,招式(一定要将着两招融会贯通，包您打遍天下无敌手)
EXAMPLE;
a.What are the valid Host ID's for 199.37.2.33/29?
Below is avery easy to use shortcut that requires no binary math
Figure out the mask :/29=248
Figure out the subnet mask multiple 256-248=8
Subnet are 8 16 24 32 40 48 etc
This is subnet32,next subnet is 40.so the broadcast address is 39
Everything between the subnet (32)and broadcast (39) are the valid hosts.
In this example .based on the given mask the valid host ranges are
33-38
b.What subnet is the host 200.1.1.130/28 on ?
A.200.1.1.128
B.200.1.1.32
C.200.1.1.16
D.200.1.1.64
E.200.1.1.0
Shorhand /28=4 bits in the last octet=decinal 255.255.255.240
Shortcut take 256-240=16
Valid subnets are mutiples of 16 32 48 64......etc
Shortcut #2
Because it's a small slice and a big number.who wants to count up every 16 bits to find the next subnetwork address ?
Just drivide 130/16=8 bits
Now take 8*16 bits = 128.so 130 is on the network 128