# 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.

<table id="bkmrk-segmentation-ip-pool"><thead><tr><th></th><th>Segmentation IP pool</th><th>AHV VM network IPAM pool</th></tr></thead><tbody><tr><td>Addresses</td><td>CVM (and host) backplane/service vNICs</td><td>User VMs on an AHV-managed network</td></tr><tr><td>Configured in</td><td>Settings → Network Configuration → Internal Interfaces (or Prism Central Network Segmentation)</td><td>Prism → Network Config → the VM subnet, or `acli`</td></tr><tr><td>Routable?</td><td>No for Backplane, yes for Service/DR</td><td>Depends on the VM network's own VLAN</td></tr><tr><td>Assignment</td><td>Automatic, one IP per CVM/host, no DHCP involved</td><td>Nutanix-managed DHCP hands addresses to VMs on boot</td></tr></tbody></table>

#### 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:

```bash
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:

```bash
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.