It's been 5 years since I've studied/brushed up on my subnetting skills so i'm a bit rusty. I have run into an issue in one of my offices. The main interface is currenlty running on 192.168.5.1/255.255.255.0 for about the last 4 years. We have since doubled our staff in the office and between the servers, phones and employees, we've quickly run out of IPs.

I'm trying to expand the network now so I can at least double the IP Space available.

Using classless ip routing, can I expand the network to allow for 510 maximum addresses by adjusting the interface to 192.168.4.1/255.255.254.0? Would I run into any issues? We're currently using a FortiGate200A Firewall if that matters.

If this would work, I could simply adjust the default route to 4.1 and update the DHCP server to include the new addresses.

I thank anyone ahead of time for responding.

You wouldn't run into any problems... the only thing is you need to adjust the subnet of all your clients on that subnet, else they would try to connect over your gateway when connecting to a host which falls into the /23 subnet. If you have a DHCP scope it is pretty easy. Just change the scope to a /23 instead of a /24.

On your firewall, most of the time you configure the subnet behind your firewall, be sure to have the subnet changed on your firewall too.

As Chojin said, you wont run into serious problems. Just bear in mind that the more you enlarge a subnet, the wider it's broadcast domain will get. This means that when ever a host sends say an ARP request, every one will hear it.

If you have to do more and more enlargements in future, I would start thinking about subneting it into separate VLANs and do routing between them. A second reason to do this, would be to isolate your servers from the rest of your department and be able to apply IP level policies (if that is needed).

But again, nothing wrong with /23 scope

Hello Guys according to that issue i think that when including a path to the cisco router, you need to specify the subnet cover up for the system. If you add the subnet cover up and execute a Display IP Tracks control, the desk reveals the systems with their next hop and the subnet covers. This will allow you to called ping any system on the subnetwork.Thanks a lot!!


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