ZyXEL Communications P-660R-D Series - Manual (Page 181)

P-660R-D Series User’s Guide
Appendix E IP Addresses and Subnetting 5
Host IDs of all zeros represent the subnet itself and host IDs of all ones are the broadcast address for that
subnet, so the actual number of hosts available on each subnet in the example above is 2
7
– 2 or 126 hosts
for each subnet.
192.168.1.0 with mask 255.255.255.128 is the subnet itself, and 192.168.1.127 with mask
255.255.255.128 is the directed broadcast address for the first subnet. Therefore, the lowest IP address that
can be assigned to an actual host for the first subnet is 192.168.1.1 and the highest is 192.168.1.126.
Similarly the host ID range for the second subnet is 192.168.1.129 to 192.168.1.254.
Example: Four Subnets
The above example illustrated using a 25-bit subnet mask to divide a class “C” address space into two
subnets. Similarly to divide a class “C” address into four subnets, you need to “borrow” two host ID bits to
give four possible combinations (00, 01, 10 and 11). The subnet mask is 26 bits
(11111111.11111111.11111111.11000000) or 255.255.255.192. Each subnet contains 6 host ID bits,
giving 2
6
-2 or 62 hosts for each subnet (all zeroes is the subnet itself, all ones is the broadcast address on
the subnet).
Subnet Address:
192.168.1.128
Lowest Host ID: 192.168.1.129
Broadcast Address:
192.168.1.255
Highest Host ID: 192.168.1.254
Table 72 Subnet 1
IP/SUBNET MASK NETWORK NUMBER
LAST OCTET BIT
VALUE
IP Address 192.168.1. 0
IP Address (Binary) 11000000.10101000.00000001. 00000000
Subnet Mask (Binary) 11111111.11111111.11111111. 11000000
Subnet Address: 192.168.1.0 Lowest Host ID: 192.168.1.1
Broadcast Address:
192.168.1.63
Highest Host ID: 192.168.1.62
Table 73 Subnet 2
IP/SUBNET MASK NETWORK NUMBER
LAST OCTET BIT
VALUE
IP Address 192.168.1. 64
IP Address (Binary) 11000000.10101000.00000001. 01000000
Subnet Mask (Binary) 11111111.11111111.11111111. 11000000
Subnet Address: 192.168.1.64 Lowest Host ID: 192.168.1.65
Broadcast Address: 192.168.1.127 Highest Host ID: 192.168.1.126
Table 71 Subnet 2 (continued)
IP/SUBNET MASK NETWORK NUMBER LAST OCTET BIT VALUE