Custom subnetting in Windows breaks network connectivity

[aragon]

I find that custom subnet mask works in Unix/Linux but not Windows.
Here is my problem:
I need many more IP addresses than my class C subnet will allow.
192.168.192.0 mask 255.255.255.0
Windows server is 192.168.192.2 mask 255.255.255.0
Router is 192.168.192.1 mask 255.255.255.0
DHCP scope 192.168.192.10=>192.168.192.250

I don't want to reconfigure any static addresses already in this segment.

I have tried the following with changes to my DHCP scope:
Windows server 192.168.192.2 mask 255.255.0.0
Router is 192.168.192.1 mask 255.255.0.0

DHCP scope:
192.168.109.1=>192.168.110.255 mask 255.255.0.0

The problem is Windows hosts do not reply when pinged from other Windows hosts using this configuration.

 

[itsp1965]

This is because the 192.168.x.x subnet's default mask is 255.255.255.0 (Class C IP address). What you did is "illegal" for a class C address, you cannot remove an entire octet for a subnet mask. If you would like to have more hosts/networks you have to modify the third octet ex) a subnet mask of 255.255.254.0 will yield 510 hosts. I would recommend you download an IP calculator to figure out what is appropriate for your environment. Hope this helps.

 

[aragon]

Actually I did manage to make this work with one small change to the DHCP scope.
My Linux DHCP server hands out IP addresses in reverse order starting at 192.168.110.255
I changed the end scope range to 192.168.110.254
Windows apparently did not like the .255 host address and I guess interpretted this as illegal (broadcast address). Although I would have thought the broadcast address for my illegal mask should have been 192.168.255.255.

Other than this small change to DHCP everything works fine with the 192.168.0.0/16 mask.
You are correct though a 255.255.254.0 or 255.255.252.0 mask makes more sense.

 

[aragon]

Just a follow up question.
The information above was not entirely accurate (some of the IP addresses were changed for anoniminity.
Here are the correct IP's with some proposed changes.
192.168.111.0 mask 255.255.255.0
Windows server is 192.168.111.2 mask 255.255.255.0
Router is 192.168.111.1 mask 255.255.255.0
DHCP scope 192.168.111.10=>192.168.111.250

I don't want to reconfigure any static addresses already in this segment.

I propose the following with changes to my DHCP scope:
Windows server 192.168.111.2 mask 255.255.252.0
Router is 192.168.111.1 mask 255.255.252.0

DHCP scope:
192.168.108.1=>192.168.110.255 mask 255.255.252.0

My new problem:
A static route exists for 192.168.111.0 mask 255.255.255.0 from two remote locations.
Is it OK to build these routes on the remote routers?
I.E. will additional routes need to be created on the router for the 108 109 110 octets created by using a 22 bit mask?

Example will this route built on a remote Cisco router also handle the additional 3rd octets?
192.168.108.0 mask 255.255.252.0 192.168.2.1