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How crucial is subnet mask in this situation?

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tschaps
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 192.168.0.0/16 giving a subnet mask of 255.255.0.0 (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 192.168.1.10-254, but giving the 255.255.0.0 subnet mask. The core switch has a static IP of 192.168.1.5, but someone set the subnet mask to 255.255.255.0.

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 192.168.0.0/16 but it only distributes addresses in the range of 192.168.1.0/24, 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.
2 REPLIES
serpel
Trusted Contributor
Solution

Re: How crucial is subnet mask in this situation?

hi,
in layer 2 networks the ip of the switch is only for managing the switch. this means that there are no problems with the subnetmask.
the only thing is that probably the switch can only be managed from devices with ip's in the 192.168.1.0/24 subnet.
hth
alex
Pieter 't Hart
Honored Contributor

Re: How crucial is subnet mask in this situation?

I agree with ABE.

As this switch does not act as router (there apears to be another default-gateway 192.168.1.1 ) the adress 192.168.1.5/24 probably only is used for management.
If this subnet is used on a single vlan all devices within 192.168.0.0/16 can communicate with eachother.

Are the performance problems within this school's local network or in the connection to the outside?
In the last, i would investigate the config of 192.168.1.1.
you mention the 5304XL as "coreswitch" wich means other network components are involved ?