> For the complete documentation index, see [llms.txt](https://prosbcdocs.telcobridges.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://prosbcdocs.telcobridges.com/configuration-details/configuration-by-use-case/local-site-survivability.md).
# Local Site Survivability
Configuration steps to enable Local Site Survivability on a SIP Registration Domain.
For what the feature does, how it behaves during an outage, its timing and its limitations, see the [Local Site Survivability](/use-cases/applications/local-site-survivability.md) use case.
### Configuration steps
1. Follow the instructions for [Configuring a Hosted PBX](/configuration-details/configuration-by-use-case/configuring-a-hosted-pbx.md).
2. Make sure SIP polling is enabled: **Poll Remote Proxy** on the registrar's NAP. Saving the domain fails if it is not. See [SIP NAP Polling](/configuration-details/configuration-by-web-portal-category/network-access-points-nap/sip-nap-polling.md).
3. Set **SIP Domain → Forwarding Parameters → Local Site Survivability** to **Cached contacts only**.
4\. Change the default register values on the domain:
| Parameter | Set to |
| ---------------------------- | ---------------------------- |
| Default Contact Expiration | 60 seconds (default: 1 hour) |
| Minimum Contact Expiration | 30 seconds |
| Maximum Contact Expiration | 60 seconds (default: 1 hour) |
| Minimum Registrar Expiration | 1 hour |
Save and apply the configuration.
### Troubleshooting
#### Confirming the domain state
The SIP registration domain has a fourth state, **Survivability**, alongside Unknown / Up / Down. Check it in this order.
**1. Web portal.** Open the **Status** page and select the **Sip** tab. The tab shows a warning color when at least one domain is in survivability, with a *Domain survivability list* between the up and down lists. The tab turns red if any domain is down, which takes priority over the survivability warning color. Available from ProSBC 4.0.2.
**2. tbstatus.** The same state is available from the CLI:
```
tbstatus /sip_registration/domain/registrar
```
**3. Gateway log.** The domain state transition is the line to grep for. It appears at REG trace level 1, in the gateway log under `setup//apps/gateway/`:
```
TBLV1 REG : State changed (Up => Survivability)
TBLV1 REG : State changed (Survivability => Up)
```
The pair confirms that recovery is automatic — nothing was configured or touched between them.
A `User request timeout` line shows a stalled forwarded REGISTER doing the down-detection instead of an OPTIONS poll, which is how the situation is recognized in the field.
#### Viewing the current registered users
The cached contacts are what the domain serves from during an outage, so the registered-user list is the second thing to check on a ticket: a user missing from it will be rejected with `480 Temporarily Unavailable` while the registrar is down.
```
tbstatus /sip_registration/domain/user
```
Routing scripts read the same data through `params[:registered_user]` and `params[:calling_registered_user]`. See [Accessing Information about Registered Users](/configuration-details/configuration-by-web-portal-category/routing-scripts/development-guides-and-tutorials/accessing-information-about-registered-users.md) for the fields each contact exposes.
#### Confirming the polling prerequisite is running
`tbstatus /nap` confirms that polling is not merely configured but actually going out:
```
- availability_percent 100
- availability_detection_struct
|- poll_remote_proxy Yes
|- is_available Yes
|- time_since_polling 51s
```
`poll_remote_proxy` confirms the setting and `time_since_polling` confirms polls are being sent. `tbstatus /system/naps` gives the same answer as an available and unavailable NAP list.
### Related pages
* [Local Site Survivability (use case)](/use-cases/applications/local-site-survivability.md)
* [Configuring a Hosted PBX](/configuration-details/configuration-by-use-case/configuring-a-hosted-pbx.md)
* [SIP registration forwarding](/configuration-details/configuration-by-use-case/sip-registration-forwarding.md)
* [Creating a SIP Domain](/configuration-details/configuration-by-use-case/sip-registration-forwarding/creating-a-sip-domain.md)
* [SIP NAP Polling](/configuration-details/configuration-by-web-portal-category/network-access-points-nap/sip-nap-polling.md)
* [Accessing Information about Registered Users](/configuration-details/configuration-by-web-portal-category/routing-scripts/development-guides-and-tutorials/accessing-information-about-registered-users.md)
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:
```
GET https://prosbcdocs.telcobridges.com/configuration-details/configuration-by-use-case/local-site-survivability.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.
