03-08-2006 02:21 AM - edited 03-03-2019 02:10 AM
when subnetting , say a 240 mask, you create the 16, 32,48 networks etc, what happens from 0 to 16, is this useable and if not why not ?
03-08-2006 02:26 AM
In older IOS version the subnet zero was not usable.
When CIDR was introduced to allow sub-subnetting the command "ip subnet-zero" was introduced to configure the use of the zero subnet.
The answer is yes, you can use the subnet 192.168.1.0/28 for instance.
HTH
Leon
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03-08-2006 03:33 PM
ok, thankyou, can you give me an example of this, so your saying if you issue the command ip subnet zero, you can make use of the 0 to whatever the start of the first subnet is ?
thanks
03-12-2006 04:19 AM
Correct. If "ip subnet-zero" is not configured (it is configured by default) you will get an error message as follow:
R1(config)#int e0/0
R1(config-if)#ip address 192.168.1.1 255.255.255.240
Bad mask /28 for address 192.168.1.1
And now after configuring "ip subnet-zero":
R1(config-if)#ip subnet-zero
R1(config)#int e0/0
R1(config-if)#ip address 192.168.1.1 255.255.255.240
R1(config-if)#
Hope this helps,
03-12-2006 03:34 AM
Nevermind,
Leon answered already.
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