Help setting up multiple IP ranges on same subnet

Question

So long story short. We setup our network YEARS ago, when we were a small company of only 10 people. Now, we are pushing 100 employees, and my network has outgrown itself.

Originally, I setup the IP Range: 192.168.16.x/24, Mask 255.255.255.0.

The problem is, I don't want to change the subnet, as changing our security infrastructure to a new subnet is a nightmare.

My question is: can I add

• 192.168.10.x/24 Subnet 255.255.255.0
• 192.168.20.x/24 Subnet 255.255.255.0

to my IP range if I have layer-3 HP switches?

I have 4 switches:

1. HPE 1920-24G Switch
2. HP 1920-48G
3. HP V1910-48G
4. HP V1910-48G

If I make a switch my gateway (192.168.16.106), and set a static route on my firewall to send all 192.168.10.0/24 to that switch, then wouldn't the layer-3 switch just route the traffic for me?

I know this is not a fix, but I'm not going to have the time or resources to fix this problem until late next year, and I need a band-aid for now.

Answer 1

There are a couple of things you could do:

• Change the network mask to expand the address range. For example, change the mask length to /23 to double , or /22 to quadruple, the number of network addresses. This is really less than ideal.
• Add VLANs. Each VLAN could have a separate network. If all your switches are layer-3 switches, you should be using those for LAN routing. You have not detailed your topology, but there are a few ways you could do this.

No matter what, you are going to need to change your security to take into account the new address range. The firewall is going to need to know all the new addressing so that it will not discard traffic to or from networks that it doesn't know. If it is performing NAT, it will need to know to NAT those source addresses, too.

If I make a switch my gateway (192.168.16.106), and set a static route on my firewall to send all 192.168.10.0/24 to that switch, then wouldn't the layer-3 switch just route the traffic for me?

Your proposed gateway (192.168.16.106) is not on the same network (192.168.10.0/24) as the hosts which will use it. Your host gateway needs to be set in the same network as the host is. The host gateway is used to send traffic destined to a different network because the host doesn't know how to get to the different network. How do you send traffic destined for a different network to a gateway on a different network if you don't know how to get to the different network in the first place?