Subnetting question

[maniac79]

Hello, this is probably not a good question and not possible but thought I'd still ask.

I've got a /26 network and I have a decent amount of IP's that I don't use. I am wanting to setup a test environment with a /29 subnet. If I was to take a group of 8 IP's x.x.x.112-.119 can I subnet that off and then setup a router with the ip of vlan x of x.x.x.111/26 and then vlan xx the ip of x.x.x.113/29 and then do a default route of 0.0.0.0 0.0.0.0 x.x.x.65?

I am not using the IP's x.x.x.111-.119

Thanks

[Giuseppe Larosa · Accepted solution]

Hello maniac79,

overlapping addresses /subnets are not supported.

You can take your /26 subnet and you can further make subnets of it, but you cannot keep the original configuration in place.

The first thing you can do is to split the /26 in two /27 subnets.

And then you can use the two subnets in different interfaces / Vlans.

x.x.x. 0     first /26 subnet

x.x.x.64  second /26 subnet

x.x.x.128 third /26 subnet

x.x.x.192 fourth /26 subnet

So you take x.x.x.64/26 and you can get

x.x.x.64/27    first /27 subnet

x.x.x.96/27    second /27 subnet.

>> I am not using the IP's x.x.x.111-.119

This will be on the new second /27 subnet x.x.x.96/27

Note: you need to change addressing on all existing hosts because of the netmask change and all device with IP addresses greater then x.x.x.97 will end in the new second /27 subnet.

x.x.x.65 default gateway for x.x.x.64/27

x.x.x.97 default gateway for x.x.x.96/27

You need to follow the binary math when subnetting

Hope to help

Giuseppe

[Edwin Portillo]

Hi my friend,

You can take as a reference to divide the network / 26 the following:

Need	Stand	CIDR	Mask	ID	Range	Broadcast
14	16	/28	255.255.255.240	192.168.1.64	192.168.1.65 - 192.168.1.78	192.168.1.79
13	16	/28	255.255.255.240	192.168.1.80	192.168.1.81 - 192.168.1.94	192.168.1.95
10	16	/28	255.255.255.240	192.168.1.96	192.168.1.97 - 192.168.1.110	192.168.1.111
7	16	/28	255.255.255.240	192.168.1.112	192.168.1.113 - 192.168.1.126	192.168.1.127

Note that the division process must be initiated by the largest network to reach the smallest in your case you have / 26 with 64 host for that reason must be smaller networks.