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How crucial is subnet mask in this situation?

Valued Contributor

How crucial is subnet mask in this situation?

I am trying to help a small school with some network issues. They use a 5304XL as their core switch. Their network range was set up giving a subnet mask of (overkill for a school with 150 computers, I know). As far as I could tell on first visit, their DHCP server is distributing only in the range of, but giving the subnet mask. The core switch has a static IP of, but someone set the subnet mask to

As they did a lot of the work themselves, I don't want to go in as a know it all (at least until I check my facts ;), and I don't want to embarrass anyone, but if the scope on the network is set to but it only distributes addresses in the range of, would this core switch set to static IP in that /24 subnet be causing performance problems?
And what if there are actually some devices with IPs outside the /24 range, does the subnet of the switch really matter, or is traffic routed via MAC address?

Thanks in advance.
Regular Advisor

Re: How crucial is subnet mask in this situation?


It would probably work - however, the client would send ARP requests to find corresponding MAC address on its own subnet (here: /16). Thus, it could never reach something within this /16 that is not within the /24 in question. If the client believes the target is on another subnet, it forwards the request to its default gw (.5).

There should be no problem changing the mask on the DHCP server though.