Re: 255.255.254.0 subnet mask vs 255.255.255.0 subnet mask

The difference is really just the number of hosts you can have on the subnet.
255.255.255.0 can have 254 hosts (i.e., 192.168.0.1 - 192.168.0.254)
255.255.254.0 can have 510 hosts (i.e., 192.168.0.1 - 192.168.1.254)

As long as all of your hosts on the DMZ have the same first 3 octets of their IP address, you should be fine. If any do have a different 3rd octet, they will be broken after the mask change.

Does that help?

Clay Carley

On 2019-01-03 11:37, Rob Berendt wrote:

Network guy had me set up our DMZ based LPARs with a 255.255.254.0 mask.
Now he wants me to change it to a 255.255.255.0 subnet mask.
I told him that it would have to wait until our next scheduled downtime.
Which is in March.

I am trying to figure out why. I can't get an explanation from him that I
can understand. Knowing why might help me to determine what I should test
to see what it broke. For example, since he discovered this by analyzing
traffic I am assuming that something is using this.

Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1
Group Dekko
Dept 1600
Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com