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Lack of IPs

Hi Guys,

I am a admin the VLANs of the company. The issue is that in the 20 VLAN is plenty of ips. 

VLAN 20 -

VLAN 21 -

VLAN 22-

I have checked that in the segment only use 192 from 256 availabilities. Then I want to change the mask on vlan 20 so:

VLAN 20 -

VLAN 22 -

VLAN 21-


I would have to change all ips in the 21 VLAN because ip and mask are differents. But in the 20 VLAN (Only change mask) should to change also the all ips? 


Thanks, #CCNP CSCO11962956

Hi there,I would have to ask

Hi there,

I would have to ask why you are going through a re-subnetting exercise with RFC1918 addresses? It only really makes sense to do this work with public IP addresses which are scarce.

Your current subnets are by no means large so will not suffer from a large amount of broadcast taffic, making them smaller will not provide much benefit.





If you make changes like this

If you make changes like this you would have to change all of the clients' subnet masks too. The reason being that devices will wrongly consider devices with certain IP addresses to reside in their subnet.