Hi,

A .240(/28) has 16 hosts per subnet a .248(/29) subnet only has 6 hosts. A /24 is a subnet of 255.255.255.0 with 254 hosts

ip address 10.101.19.10 255.255.255.0
ip address vlan 7

change to this

ip address 10.101.19.1 255.255.255.248
ip address vlan 7

Would that then fix the error I'm getting when I attempt to change vlan 1 to 255.255.248.0?

So, to be clear, vlan 7 is our management vlan, and that's currently vlan 7 with an ip of 10.101.19.1 with a mask of 255.255.255.0.

The vlan I'm interested in changing in vlan 1 which is 10.101.2.1 with a mask of 255.255.240.0. I'd like to change that to 255.255.248.0

Thanks for the reply. 

VLAN 1 already has an IP address:

interface vlan 1

routing

ip address 10.101.2.1 255.255.240.0

exit

I just want to change the subnet mask to 248 but whenever I attempt to do it I get;

Error! Subnet conflict between specified IP Address and current configuration. All routing interfaces, service ports and network ports must be configured on different subnets.

Which I don't get because I don't have another subnet with that mask, nor do I have any IP addresses in that range.

Much appreiciated.

Oh ok, no, that would change VLAN 7. For VLAN 1 how are you changing it? Are you removing the existing IP with no ip address and then putting the new one on?

.240 includes .248 so it sees the conflict there, you have to remove the existing IP first.

Ok so to be clear, I'd have to remove the subnet 255.255.240.0 subnet mask completely, save it, then add 255.255.248.0?

Edit: I'm doing these changes in dell openmanage btw, so I'm not sure it'll let me clear out my subnet mask completely.