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Vantage RADIUS User’s Guide
IP Subnetting
H-3
Since the mask is always a continuous number of ones beginning from the left, followed by a continuous
number of zeros for the remainder of the 32 bit mask, you can simply specify the number of ones instead of
writing the value of each octet. This is usually specified by writing a “/” followed by the number of bits in
the mask after the address.
For example, 192.1.1.0 /25 is equivalent to saying 192.1.1.0 with mask 255.255.255.128.
The following table shows all possible subnet masks for a class “C” address using both notations.
Chart H-4 Alternative Subnet Mask Notation
SUBNET MASK IP ADDRESS
SUBNET MASK “1” BITS
LAST OCTET BIT VALUE
255.255.255.0 /24
0000
0000
255.255.255.128 /25
1000
0000
255.255.255.192 /26
1100
0000
255.255.255.224 /27
1110
0000
255.255.255.240 /28
1111
0000
255.255.255.248 /29
1111
1000
255.255.255.252 /30
1111
1100
The first mask shown is the class “C” natural mask. Normally if no mask is specified it is understood that
the natural mask is being used.
Example: Two Subnets
As an example, you have a class “C” address 192.168.1.0 with subnet mask of 255.255.255.0.
NETWORK NUMBER
HOST ID
IP Address
192.168.1.
0
IP Address (Binary)
11000000.10101000.00000001. 00000000
Subnet Mask
255.255.255.
0
Subnet Mask (Binary)
11111111.11111111.11111111. 00000000
The first three octets of the address make up the network number (class “C”). You want to have two
separate networks.
Divide the network 192.168.1.0 into two separate subnets by converting one of the host ID bits of the IP
address to a network number bit. The “borrowed” host ID bit can be either “0” or “1” thus giving two
subnets; 192.168.1.0 with mask 255.255.255.128 and 192.168.1.128 with mask 255.255.255.128.
Summary of Contents for VANTAGE RADIUS 50
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Page 65: ...RADIUS Server II Part II RADIUS Server This part introduces the RADIUS Server screens ...
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