Please help me with my sub netting concept...
what 10.2.1.1/9 mean?
Here is a basic netmask table:
ID # Bits Number Hosts Usable Hosts Netmask Note
6 /6 67108864 67108862 252.0.0.0
7 /7 33554432 33554430 254.0.0.0
8 /8 16777216 16777214 255.0.0.0 Class A Network
9 /9 8388608 8388606 255.128.0.0
10 /10 4194304 4194302 255.192.0.0
11 /11 2097152 2097150 255.224.0.0
12 /12 1048576 1048574 255.240.0.0
13 /13 524288 524286 255.248.0.0
14 /14 262144 262142 255.252.0.0
15 /15 131072 131070 255.254.0.0
16 /16 65536 65534 255.255.0.0 Class B Network
17 /17 32768 32766 255.255.128.0
18 /18 16384 16382 255.255.192.0
19 /19 8192 8190 255.255.224.0
20 /20 4096 4094 255.255.240.0
21 /21 2048 2046 255.255.248.0
22 /22 1024 1022 255.255.252.0
23 /23 512 510 255.255.254.0
24 /24 256 254 255.255.255.0 Class C Network
25 /25 128 126 255.255.255.128
26 /26 64 62 255.255.255.192
28 /28 16 14 255.255.255.240
27 /27 32 30 255.255.255.224
29 /29 8 6 255.255.255.248
30 /30 4 2 255.255.255.252
First of all, this is an IPv4 address; IPv4 address consists of 32 bits.
The /9 represents the number of bits for the network, meaning that they are reserved for the network, and you can't use them. So by a simple calculation,the number of bits for the hosts in this network is (32 - 9 = 23) and the number of hosts of this network is 2^23 - 2 Hosts ( we subtract 2 because one address is for the network address and the other is the broadcast address for the network)
is 192.168.0.1/8 is allowed? I have many tutorial which allow atleast 24 for this....
But an ip calculator calculate the above question.
Its called Classless Inter-Domain Routing (CIDR). More info here:
http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing
For more subnetting information:
http://www.punkwalrus.com/howto/subnetting.html
Hope this helps.
Hello Majestics,
Theoretically 192.168.0.1/8 is not allowed as a private network, since the network 192.168.x.x/16 is the private network, however if you want to use a private network with /8 you can use the 10.x.x.x/8.
What is meant by private network is a network that will not pass the gateway of the network. i.e. if you have for example a packet that has 192.168.1.10 (suppose that it is a host) as a destination, when it reaches the router or the gateway, it will be redirected to the local network, meaning it will not go through the gateway of the network and to the public network (internet).
But suppose you used 10.x.x.x/8 in your private network, then you have 2^24 - 2 hosts, and that is impossible to have in one network, thus you will have plenty and plenty of unused hosts, which brings us back to the reason of variable length subnet mask (VLSM) and classless Networks.
The reason behind the subnetting is because of the depletion of IPv4 addresses, because of huge network of hosts that was based on classfull networks as a class A network (refer to rch1231 post above).
Hope this helps in understanding subnetting.
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