IP Pools

Two different "IP pools" — don't mix them up

Nutanix reuses the term "IP pool" for two unrelated things. Both come up when you're doing backplane/segmentation work, but they address completely different traffic.

Segmentation IP pool (Backplane / Service)

When you enable Backplane or Service segmentation, Prism asks for a start/end range, e.g.:

192.168.21.11 - 192.168.21.20

Size it for the cluster's current node count plus headroom for future expansion — one address is consumed per CVM (and, on current AOS, per AHV host) for each segmented traffic type. There's no reuse or lease/DHCP mechanism here: once an address is assigned it stays assigned until the interface is reconfigured.

AHV VM network IPAM pool

Separate from the above — this is Nutanix-managed DHCP for guest VMs on a given AHV network, already referenced on Important Commands in this book:

acli net.create <name> vlan=<vlan_id> ip_config=<subnet/prefix>

The command above only creates the network/subnet — the actual address pool for it is added separately:

acli net.add_dhcp_pool <name> start=<first_ip> end=<last_ip>

or in Prism: the VM network's config page → "IP Address Pools" → Create Pool.

Gotcha: .254 in the subnet is reserved for the Acropolis DHCP server itself if you didn't explicitly set a DHCP server address when creating the network — don't include it in the pool range.

This pool has nothing to do with the CVM/host backplane above — it only ever hands out addresses to VMs that sit on this particular AHV network.