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docs: clarify host=0.0.0.0 causes controller to register as 127.0.0.1

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Add details about the "No common subnet" error when Controller's host
is set to 0.0.0.0, and how to verify via /v3/version endpoint.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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YueGuobin 2026-04-25 15:54:12 +08:00
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19
docs/features/compute-controller-setup.md
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@ -71,8 +71,10 @@ POST /v3/computes
### Host Configuration
- **Controller `host`**: If set to `0.0.0.0`, it will be changed to `127.0.0.1`, which breaks cross-subnet link creation
- **Solution**: Always use the actual IP address for Controller's `host` field
- **Controller `host`**: If set to `0.0.0.0`, the controller will register itself as `127.0.0.1`, which breaks remote compute connections
- **Symptom**: Compute nodes report "No common subnet for compute X (controller) and Y" even when on the same network
- **Solution**: Always use the actual LAN IP address for the Controller's `host` field (e.g., `host = 192.168.1.104`)
- **Dynamic IP**: If the controller machine uses DHCP, set a static lease on the router or use mDNS (`.local` domain)
### Password Configuration
@ -99,9 +101,16 @@ POST /v3/computes
### No Common Subnet Error
1. Verify Controller's `host` is set to its actual IP, not `0.0.0.0`
2. Ensure both machines are on the same network
3. Check firewall rules allow UDP communication
If compute nodes report:
```
Cannot get an IP address on same subnet: No common subnet for compute X (controller) and Y
```
1. **Primary cause**: Controller's `host` is set to `0.0.0.0` - it registers as `127.0.0.1` which is unreachable from compute nodes
2. Check the controller's `/v3/version` endpoint - if `controller_host` shows `127.0.0.1`, this is the issue
3. Set the Controller's `host` to its actual LAN IP address (e.g., `192.168.1.104`)
4. Verify both machines are on the same network and can ping each other
5. Check firewall rules allow TCP/UDP communication on required ports
### Controller Hostname Unreachable