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# SIP

The **Advanced SIP Settings** view lets you configure detailed parameters for your [SIP](/glossary/s/sip) services.

##

^ Item ^ Description ^
| Sip Proxy servers | [Proxies](/glossary/p/proxy) to allow incoming calls from. |
| Bind Interface | Restrict listening to particular WAN interface. |
| Bindport | [Port](/glossary/p/port) to use for [UDP](/glossary/u/udp) listening. |
| User Agent | Custom `User-Agent` information in the SIP header. |
| RTP Port Range | [Ports](/glossary/p/port) to use for [RTP](/glossary/r/rtp) |
| DTMF Mode | Mode for [DTMF](/glossary/d/dtmf_mode) (`Compatibility` / `RFC 2833` / `SIP INFO` / `Inband`). |
| Register Interval | Time in seconds between registration attempts. |
| Realm | [SIP Realm](/glossary/s/sip_realm) for digest authentication. |
| Localnet | Network addresses that are considered inside of the [NAT](/glossary/n/nat) network. |
| Register Attempts | Number of registration attempts before giving up. |
| Register Timeout | Time before giving up a registration attempt. |
| Register Back-off Attempts | Number of attempts before [back-off](/glossary/b/backoff). |
| Register Back-off Timeout | Time in [back-off](/glossary/b/backoff) before giving up attempt to register. |
| Remote Hold | Send hold events to proxy (Let network handle music on hold). |
| SRV Lookup | Enable DNS [SRV](/glossary/s/srv) lookup. |
| DNS Manager | Enable [Asterisk](/glossary/a/asterisk) DNS manager. |
| DNS Manager Refresh Interval | Refresh interval for the DNS manager. |
| Line suffix in contact header | Add suffix to SIP contact header with information about called lines. |
| SIP DiffServ | [Differentiated services](/glossary/d/diffserv) type of service for SIP data. |
| Audio DiffServ | [Differentiated services](/glossary/d/diffserv) type of service for audio data. |
| Congestion tone | Tone to play on congestion.  (`Congestion` / `Info`) |
| STUN server | [STUN](/glossary/s/stun) service provider. |
| TLS/SSL Version | [TLS v1](/glossary/t/tls) / [TLS v2](/glossary/s/ssl) / [TLS v3](/glossary/s/ssl). |
| Cipher string | [Cipher](/glossary/c/cipher) identifier string. |
| Trusted CA | Public key for a trusted [Certificate Authority](/glossary/c/ca). |


### Trusted CA Certificate

To add a Trusted CA Certificate key:

* Click **Add**

* Copy the public key

* Paste the key into the window

* Click **Save**

* Click **Apply**