Networks created within the openstack platforms are not routed through NTNU, thus in theory it is not important which subnet is selected. It might however be a problem if your virtual machine needs to contact external resources and you have provision your virtual machines within the same address range that is currently being use elsewhere, causing your local address range to overlap with the address range of another network. Because of this, it is common practice to use the address ranges specified in the RFC1918 (a.k.a IPv4 Private Address Space):
- 10.0.0.0/8
- 172.16.0.0/12
- 192.168.0.0/16
- tl;dr - use a subnet from this range to avoid any weird issues → 192.168.N.0/24 where N is a number from 0 and 255.
RFC1918 within NTNU
NTNU is however using the following subnets within the RFC1918 range, therefore their use should be avoided:
10.0.0.0/8 - Large pieces of this range is already in use; and this block is likely to be used in new subnets within NTNU as well. The general purpose floatin-IP's assigned in openstack is also from this range, and it can thus involve a bit of confusion if both the vm's IP and the floating-ip looks the same. It is thus recommended not to use this block at all.
- 172.17.0.0/16