Assigning IPv6 address to prefix from available pool starts from 0 instead of 1

[bctiemann]

NetBox Edition

NetBox Community

NetBox Version

v4.5.1

Python Version

3.12

Steps to Reproduce

Here are the steps to recreate.
Step 1: Create an RIR (if you don’t already have one)
IPAM → RIRs → Add
Name: ARIN
Private: ✔ (if internal)

Step 2: Create an IPv6 aggregate
IPAM → Aggregates → Add
Example:
RIR: ARIN
Prefix: 2001:db8::/32 (documentation range — safe for demos)
Description: Global IPv6 allocation
Step 3: Create container prefixes
IPAM → Prefixes → Add
Example:Prefix: 2001:db8:1000::/40
Status: Container

Step 4: Create an active /64
IPAM → Prefixes → Add
Example:Prefix: 2001:db8:1000:10::/64
Status: Active.

Step 5: Assign an IPv6 address
From the prefix view:
Click “Available IPs”
Select First available THIS IS WHERE THE ERROR OCCURS. When selecting it gives the error "2001:db8:1000:10:: is a network ID, which may not be assigned to an interface." Seems like it's choosing the ID and not first available IP.

(Use the "Many IPs available" button in the above view)

Expected Behavior

The IPAddress 2001:db8:1000:10::1/64 should be created (the first available non-network IP in the pool, matching the behavior of IPv4 addresses (where for example 111.112.113.1 would be allocated in a prefix of 111.112.113.0/24).

Observed Behavior

The IPAddress 2001:db8:1000:10::/64 is created, which is a network address.