0 AND 0 = 0
0 AND 1 = 0
1 AND 1 = 1
0 OR 0 = 0
0 OR 1 = 1
1 OR 1 = 1
Net ID Host ID
A class 00000000.00000000.00000000.00000000
Net ID Host ID
B class 10000000.00000000.00000000.00000000
Net ID Host ID
C class 11000000.00000000.00000000.00000000
A Class – 00000001到011111110
B Class – 10000001到101111110
C Class – 11000001到110111110
Host ID = 先將netmask NOT,再與ip AND
broadcast = 先將netmask NOT,再與ip OR
EXAMPLE1:
IP = 128.128.128.128 -> 10000000.10000000.10000000.10000000
Netmask = 255.255.0.0 -> 11111111.11111111.00000000.00000000
NetID(subnet) = IP AND Netmask -> 10000000.10000000.00000000.00000000 -> 128.128.0.0
HostID = NOT Netmask -> 00000000.00000000.11111111.11111111 -> AND IP -> 00000000.00000000.10000000.10000000 -> 0.0.128.128
Broadcast = NOT Netmask -> 00000000.00000000.11111111.11111111 -> OR IP -> 10000000.10000000.11111111.11111111 -> 128.128.255.255
EXAMPLE2:
139.175.152.254/255.255.0.0
-> 10001011.10101111.10011000.11111110
11111111.11111111.00000000.00000000
Net = ip AND netmask -> 10001011.1010111.00000000.00000000 = 139.175.0.0
HOST = NOT netmask -> 00000000.00000000.11111111.11111111
10001011.10101111.10011000.11111110
AND IP -> 00000000.00000000.10011000.11111110->0.0.152.254
Broadcast = NOT netmask -> 00000000.00000000.11111111.11111111
10001011.10101111.10011000.11111110
OR IP -> 10001011.10101111.11111111.11111111 = 139.175.255.255
二進位換成十進位
10011101 -> 27+06+05+24+23+22+01+20=128+0+0+16+8+4+0+1=157
十進位換成二進位
157/2
78/2 餘1
39/2 餘0
19/2 餘1
9/2 餘1
4/2 餘1
2/2 餘0
1 餘0
network id 全1 -> broadcast擴播
host id 全1 -> 識別網路 ex:10.130.1.0 表network id為10.130.1.z的網段
network id host id 全0 -> 0.0.0.0 裝置本身
host id 全1 -> broadcast ex:203.74.205.255 表203.74.205.0這網段的廣播封包
host id network id 全1 -> limited/local broadcast ex:255.255.255.255 限同一網段
network id 除prefix 其餘全1 -> loopback ex:127.x.y.z 191.255.x.y 223.255.255.z
C class
203.66.77.0/255.255.255.0
11001011.01000010.01001101.00000000/11111111.11111111.11111111.00000000
從Netmask借3bit割成8(23)個子網路
<————————SubnetID————————> <-HostID->
1 1 1 1 1 1 1 1.1 1 1 1 1 1 1 1.1 1 1 1 1 1 1 1.1 1 1 0 0 0 0 0 -> 255.255.255.224
有八個子網路,每個子網路有30主機(25-2),會扣掉兩個是因為203.66.77.00000000(subnet)與203.66.77.00011111(broadcast)不能用
203.66.77.00000001到.00011110(1到30)
203.66.77.00100001到.00111110(33到62)
203.66.77.01000001到.01011110(65到94)
203.66.77.01100001到.01111110(97到126)
203.66.77.10000001到.10011110(129到158)
203.66.77.10100001到.10111110(161到190)
203.66.77.11000001到.11011110(193到222)
203.66.77.11100001到.11111110(225到254)
B Class
139.175.152.254/255.255.0.0
-> 10001011.10101111.10011000.11111110/11111111.11111111.0000000.00000000
借三個 bits 11111111.11111111.1110000.00000000
Netmask = 255.255.224.0
Subnet為
10001011.10101111.00000000.00000000(139.175.0.0)
10001011.10101111.00100000.00000000(139.175.32.0)
10001011.10101111.01000000.00000000(139.175.64.0)
10001011.10101111.01100000.00000000(139.175.96.0)
10001011.10101111.10000000.00000000(139.175.128.0)
10001011.10101111.10100000.00000000(139.175.160.0)
10001011.10101111.11000000.00000000(139.175.192.0)
10001011.10101111.11100000.00000000(139.175.224.0)
IP為
139.175.00000000.00000001到139.175.00011111.11111110
139.175.00100000.00000001到139.175.00111111.11111110
139.175.01000000.00000001到139.175.01011111.11111110
139.175.01100000.00000001到139.175.01111111.11111110
139.175.10000000.00000001到139.175.10011111.11111110
139.175.10100000.00000001到139.175.10111111.11111110
139.175.11000000.00000001到139.175.11011111.11111110
139.175.11100000.00000001到139.175.11111111.11111110
2008/03/20 added
IP Address 10.1.1.2
Netmask 255.255.255.0
Subnet/Netmask: 10.1.1.0/255.255.255.0 (24)
Available IP: 10.1.1.1 ~ 254,共 254 個可用 IP (= 254 – 0)
Gateway: 10.1.1.254
IP Address 10.1.1.2
Netmask 255.255.255.128
Subnet/Netmask: 10.1.1.0/255.255.255.128 (25)
Available IP: 10.1.1.1 ~ 126,共 126 個可用 IP (= 254 – 128)
Gateway: 10.1.1.126
IP Address 10.1.1.2
Netmask 255.255.255.192
Subnet/Netmask: 10.1.1.0/255.255.255.192 (26)
Available IP: 10.1.1.1 ~ 62,共 62 個可用 IP (= 254 – 192)
Gateway: 10.1.1.62
IP Address 10.1.1.2
Netmask 255.255.255.224
Subnet/Netmask: 10.1.1.0/255.255.255.224 (27)
Available IP: 10.1.1.1 ~ 30,共 30 個可用 IP (= 254 – 224)
Gateway: 10.1.1.30
IP Address 10.1.1.2
Netmask 255.255.255.240
Subnet/Netmask: 10.1.1.0/255.255.255.240 (28)
Available IP: 10.1.1.1 ~ 14,共 14 個可用 IP (= 254 – 240)
Gateway: 10.1.1.30
IP Address 10.1.1.2
Netmask 255.255.255.248
Subnet/Netmask: 10.1.1.0/255.255.255.248 (29)
Available IP: 10.1.1.1 ~ 6,共 6 個可用 IP (= 254 – 248)
Gateway: 10.1.1.6
IP Address 10.1.1.2
Netmask 255.255.255.252
Subnet/Netmask: 10.1.1.0/255.255.255.252 (30)
Available IP: 10.1.1.1 ~ 2,共 2 個可用 IP (= 254 – 252)
Gateway: 10.1.1.2
留言