vpn director is breaking my brain

[mgg]

I'm trying to split my network up so my oracle virtualboxes go through the vpn and everything else goes through like normal. My first idea was to use another nic and route the IP for that nic through the VPN. I thought I could tell oracle VM to use that nic, but the only way you can pick which nic it should use is to set it to a bridge adapter, which appears to use whatever dhcp server that cable is attached to and get an IP from it. Since the IP doesnt match, it doesnt matter if it's going through that cable or not. When the VM's network adapter is set to NAT, you can't pick your nic so it goes through whatever the server's primary nic is. So now I'm thinking I need to set it to use the bridged adapter, script the assigning of mac addresses when i clone a new box so it's on a list of mac addresses i would expect and associate each of those mac addresses to an IP in the dhcp area... then use the vpn director to send those ips through the VPN. with the vpn director, you cant use ranges () so I'm trying to figure out this non-user friendly CIDR notation. I'm sure CIDR is intuitive for those who deal with networking all day everyday, but for your average user it is confusing AF.

I need up to 50 ips reserved for the virtualboxes so I figured I'd route the last 64ish IPs to the vpn. Each of the mac addresses that might be used needs an entry in the dhcp server, then for the vpn director i need some sort of CIDR notation to only route the last 64 (or 62) ips through the vpn.

A /24 means the whole shabang, but a /25 confuses me. i understand it makes a subnet mask of 255.255.255.128 and it splits the last 256 addresses into 2 subnets, but i cant wrap my brain around what that means in the vpn director. would 1-127 be routed to the rule or excluded from the rule?

Assuming my network is on 192.168.7.xxx, what would the cidr notation be for what i need? If I wanted the last 64 ips to go to the vpn, would it be 192.168.7.192/26? if i wanted the last 128 ips to go to the vpn, would the rule be 192.168.7.128/25?

Then if I wanted to prevent random things from getting IPs in that range, could i set the ip pool ending address to 192 and still have dhcp entries higher than 192?

 

[RMerlin]

if i wanted the last 128 ips to go to the vpn, would the rule be 192.168.7.128/25?

Yes. A subnet IPs will have the first IP of that subnet as the Network address, and the last IP as a Broadcast address. So when defining a subnet, you use the first IP as part of the CIDR address, with the appropriate mask. So with a /25, that gives you these two subnets:

192.168.7.0/25 (1 through 126)
192.168.7.128/25 (129 through 254)

 

[mgg]

Do you know if my /26 is right? I'd prefer only reserving a quarter of them.

And would setting the ip pool ending address to 192 in the dhcp area prevent me from manually assigning IPs higher than 192?

 

[RMerlin]

Do you know if my /26 is right? I'd prefer only reserving a quarter of them.

To calculate a CIDR, convert your addresses into binary. /26 means the last 6 bits will be your clients, with the first and last IP of each subnet being reserved.

192.168.0.0/26 (1 to 62)
192.168.0.64/26 (65 to 126)
192.168.0.128/26 (129 to 190)
192.168.0.192/26 (193 to 254)

And would setting the ip pool ending address to 192 in the dhcp area prevent me from manually assigning IPs higher than 192?

Yes, but to be safe, end it at 191 since 192 will be the network address of that last subnet that you will be using in VPN Director.