Gateway ip address and subnet mask

[MDeepe]

We are changing our DHCP subnet from a /16 to a /22 but we have some statically assigned ip addresses that are /16.  The gateway is still the same but the question is can we change the DHCP pool subnet and change the statically assigned address mask later?

[balaji.bandi]

If you change /22 they address beyond /22 will  not be part of this subnet, so suggest to allocate new IP address for the static one and restart the device to get new subnetmask.

[MDeepe]

Just to clarify, the statically assigned ip addresses with a /16 mask would all fall in the range of the /22 subnet.  They would just have a different mask than the gateway mask on the router.  Hope that makes more sense.

[MHM Cisco World · Accepted solution]

The mask in client make client decided to send ask GW any IP behind this mask or not. 

Now if client use /16 then any IP behind this subnet and mask 16 will send to GW, here the issue

The GW will not respond to these IP since it assume that this normal arp within /22 this make arp between clients /16 and GW /22 incomplete and hence traffic not pass.

MHM

[balaji.bandi]

i understand now - but for completeness - i will change the mask on both the side DHCP and Client.