# Trunk Parameters

Cloud Voice can export your SIP (Session Initiation Protocol) trunks to a CSV (comma-separated values) file and create trunks in bulk by importing that same format. This page describes every column in the file so you can build a valid import or make sense of an export.

:::note
Only SIP peer trunks and register trunks can be exported and imported. Account trunks are not supported.
:::

:::tip[Blank fields on import]
When you import a trunk and leave a field empty, Cloud Voice applies the value shown in the **Default** column, wherever one is listed. Fields whose default is `N/A` stay empty.
:::

## Parameters

:::note[Acronyms used in this table]
- **DID / DDI** (Direct Inward Dialing / Direct Dialing In): an external number that routes an incoming call to your phone system.
- **DOD** (Direct Outward Dialing): the outbound caller ID a user picks for a specific call.
- **DTMF** (Dual-Tone Multi-Frequency): the tones a phone keypad sends, used for menus and codes.
- **SDP** (Session Description Protocol): the media details (codecs, ports) carried inside a SIP message.
- **SRTP** (Secure Real-time Transport Protocol): encrypted call media, the secured form of RTP (Real-time Transport Protocol).
- **SIP URI**: a SIP address written as `sip:user@domain`.
:::

| Parameter | Description | Requirement | Values and rules | Default |
| --- | --- | --- | --- | --- |
| Name | Identifies the trunk. | Required | Up to 63 characters. Spaces and special characters are not allowed, and the name must be unique. | N/A |
| Trunk Status | Turns the trunk on or off. | Required | `0` (disabled) or `1` (enabled). | `1` |
| Trunk Type | The kind of trunk. | Required | `register`, `did_based`, `port_based`, or `private_network`. Account trunks cannot be imported. | `register` |
| Transport | Signaling transport agreed with the provider. | Required | Depends on Trunk Type: `port_based` allows `udp`; `did_based` allows `udp` or `tcp`; `private_network` allows `udp`, `tcp`, or `tls`; `register` allows `udp`, `tcp`, `tls`, or `dnsnaptr`. | `udp` |
| Hostname/IP | The provider's IP address or domain. | Required | Up to 255 characters. | N/A |
| Port | The signaling port for the trunk. | Required | A number from `0` to `65535`. | N/A |
| Domain | The domain used in the SIP URI of headers such as `From` and `To`. If the provider does not supply one, reuse the Hostname/IP value. | Required | Up to 255 characters. | N/A |
| Username | The account name used to register with the provider. | Required when Trunk Type is `register`. | Up to 255 characters. | N/A |
| Password | The password paired with the username. | Required when Trunk Type is `register`. | Up to 255 characters. | N/A |
| Authentication Name | The authentication identity used to register with the provider. | Optional | Up to 255 characters. | N/A |
| Enable Outbound Proxy | Whether calls are routed through an outbound proxy. | Required when Trunk Type is `register`. | `0` (disabled) or `1` (enabled). | `0` |
| Outbound Proxy Server | Address of the outbound proxy. | Required when Enable Outbound Proxy is `1`. | Up to 255 characters. | N/A |
| Port of Outbound Proxy Server | Port of the outbound proxy. | Required when Enable Outbound Proxy is `1`. | A number from `1` to `65535`. | N/A |
| Codec Setting | Audio and video codecs offered on the trunk. | Required | One or more of `ulaw`, `alaw`, `g729`, `gsm`, `h264`, `h263`, `h263p`, `ilbc`, `g722`, `g726`, `speex`, `adpcm`, `vp8`, `mpeg4`, `opus`. List them in preference order joined by `&` (for example, `ulaw&alaw`). Any unsupported entry is ignored. | `ulaw&alaw&gsm&h264&ilbc&g722&g726&g729` |
| DTMF Mode | How DTMF tones are sent. | Required | `rfc4733`, `info`, `inband`, or `auto`. | `rfc4733` |
| DTMF FMTP | The fmtp value used when DTMF Mode is `rfc4733`. | Optional | `0-16` or `0-15`. | `0-16` |
| Qualify | Whether to send SIP OPTIONS packets to check that the peer is reachable. | Required | `0` (disabled) or `1` (enabled). | `1` |
| Enable SRTP | Whether to encrypt media (RTP) on the trunk. | Required | `0` (disabled) or `1` (enabled). | `0` |
| T.38 Support | Whether T.38 fax is allowed. | Required | `0` (disabled) or `1` (enabled). | `0` |
| Inband Progress | Whether inband progress is used. | Required | `0` (disabled) or `1` (enabled). | `0` |
| Ignore 183 Message without SDP | Whether to drop 183 responses that carry no SDP. | Required | `0` (disabled) or `1` (enabled). | `0` |
| Forward the 180 (SDP) Message Following the Peer's Format | Whether Cloud Voice mirrors the far end, sending a 180 with SDP only when the 180 it received contained SDP. | Required | `0` (disabled) or `1` (enabled). | `0` |
| Dedicated Trunk | Whether the trunk needs a dedicated internal IP address to connect. | Optional | `0` (disabled) or `1` (enabled). | `0` |
| Enable SIP Authentication Cache | Whether Cloud Voice caches a successful SIP authentication and reuses it for later requests (such as `INVITE` and `BYE`) within the same session or registration cycle. | Optional | `0` (disabled) or `1` (enabled). | `0` |
| Force SIP URI Scheme | Whether to force the `sip:` scheme instead of `sips:` in registration requests, downgrading signaling from encrypted to unencrypted. Available only when Trunk Type is `register` and Transport is `tls` or `dnsnaptr`. | Optional | `0` (disabled) or `1` (enabled). | `0` |
| Ignore 100 Trying Response | Whether to ignore the `100 Trying` response. Available only when Trunk Type is `register`. | Optional | `0` (disabled) or `1` (enabled). | `0` |
| Support SIP REFER | Whether the trunk accepts SIP REFER requests. | Optional | `0` (disabled) or `1` (enabled). | `0` |
| Allow Transfer To | Destination types permitted for blind transfers driven by REFER. Available only when Support SIP REFER is `1`. | Required when Support SIP REFER is `1`. | `external_number`, `internal_number`, or `external_number&internal_number`. | N/A |
| Prefix | Prefix that Cloud Voice prepends to the REFER target number so a blind transfer matches an outbound route. Available only when Support SIP REFER is `1` and Allow Transfer To includes external numbers. | Optional | Digits and the characters `*` `#` `(` `)` `.` `-` `+`; up to 7 characters. | N/A |
| Maximum Concurrent Calls | Cap on simultaneous calls over the trunk. | Required | Digits only, up to 5 characters; `0` means unlimited. | `0` |
| Call Restriction Type | Which calls the concurrent-call cap applies to. | Required | `outbound` or `all`. | `outbound` |
| Outbound Failover SIP Code | Whether failover uses the built-in SIP codes or a custom list. When a matching code is returned, the call fails over to the next trunk on the outbound route and is retried. | Required | `default` (codes `408`, `500`, `502`, `503`, `513`, `555`, `580`) or `custom`. | `default` |
| SIP Codes | The response codes that trigger failover when Outbound Failover SIP Code is `custom`. | Required when Outbound Failover SIP Code is `custom`. | Up to 127 characters, allowing as many as 32 codes separated by `;`. Only codes in the `300`-`699` range take effect. | `408;500;502;503;513;555;580` |
| Default Outbound Caller ID | The caller ID shown on the callee's device. It must be permitted by the provider. | Optional | Digits, letters, and the characters `(` `)` `.` `-` `+` `*` `#`; up to 31 characters. | N/A |
| Default Outbound Caller ID Name | The caller ID name shown on the callee's device. | Optional | Up to 127 characters. | N/A |
| Get Caller ID From | Which SIP header the trunk reads the caller ID from on inbound calls. | Required | `follow_system`, `from`, `contact`, `rpid`, `pai`, or `ppi`. | `follow_system` |
| Get DID From | Which SIP header the trunk reads the DID from on inbound calls. Because providers place the DID in different headers, set this after inspecting the provider's SIP packets; an incorrect header causes the call to fail. | Required | `follow_system`, `to`, `invite`, `diversion`, `rpid`, `pai`, `ppi`, or `pcpid`. | `follow_system` |
| From User Part | The caller ID placed in the user part of the `From` header. | Required | `default`, `ext_cid`, `trunk_user` (register trunks only), `trunk_def_outbcid`, `ext_outbcid`, `outrounter_outbcid`, `originator_cid`, or a custom value (digits, letters, and `(` `)` `.` `-` `+` `*` `#`; up to 31 characters). | `default` |
| From Display Name Part | The caller ID name placed in the display-name part of the `From` header. | Required | `default`, `ext_cid_name`, `trunk_def_outbcid_name`, `ext_outbcid_name`, `originator_cid_name`, or a custom value (up to 63 characters). | `default` |
| Diversion | The value carried in the `Diversion` header. Leave empty to omit the header. | Optional | `default`, `ext_cid`, `trunk_user` (register trunks only), `trunk_def_outbcid`, `ext_outbcid`, `outrounter_outbcid`, `originator_cid`, or a custom value (up to 31 characters, using digits, letters, and `(` `)` `.` `-` `+` `*` `#`). | N/A |
| Remote-Party-ID | The value carried in the `Remote-Party-ID` header. Leave empty to omit the header. | Optional | Same choices as Diversion. | N/A |
| P-Asserted-Identity | The value carried in the `P-Asserted-Identity` header. Leave empty to omit the header. | Optional | Same choices as Diversion. | N/A |
| P-Preferred-Identity | The value carried in the `P-Preferred-Identity` header. Leave empty to omit the header. | Optional | Same choices as Diversion. | N/A |
| From Host Part | The domain or IP placed in the `From` field of the SIP INVITE. Applies to peer trunks only. | Required | `default` or a custom value (up to 255 characters). | `default` |
| To Host Part | The domain or IP placed in the `To` field of the SIP INVITE. Applies to peer trunks only. | Required | `default` or a custom value (up to 255 characters). | `default` |
| User Agent | The User Agent string, when the provider requires it for authentication. | Optional | Up to 255 characters. | N/A |
| Realm | The realm string presented to users so they know which credentials to use. | Optional | Up to 255 characters. | N/A |
| Send Privacy ID | Whether to include the Privacy ID in the SIP header. | Required | `0` (disabled) or `1` (enabled). | `0` |
| User Phone | Whether to append `user=phone` to the request line of the SIP INVITE. | Required | `0` (disabled) or `1` (enabled). | `0` |
| Send X-OpenAPI-Call-ID | Whether to add an `X-OpenAPI-Call-ID` header to the SIP INVITE so the Call ID travels with inbound and outbound calls routed over the trunk. | Required | `0` (disabled) or `1` (enabled). | `0` |
| 100rel | How the trunk handles 100rel (reliable provisional responses). | Required | `Required`, `Supported`, or `Disabled`. | `Disabled` |
| Maxptime | The Maxptime advertised in outbound INVITEs. | Required | `default` (Cloud Voice sends a value matching the codec used for the call) or a custom value that is a multiple of 10 from `20` to `300`. | `default` |
| Support P-Early-Media | Whether the INVITE includes the P-Early-Media header. | Required | `0` (disabled) or `1` (enabled). | `0` |
| DID/DDI | A virtual number that identifies which path of the trunk is carrying the call. | Required when Trunk Type is `register` or `did_based`. | Up to 31 characters. For `register` or `did_based`: digits, letters, and `(` `)` `.` `-` `+` `*` `#`. For `port_based` or `private_network`: digits, letters, and `[` `]` `*` `#` `(` `)` `.` `-` `+` `!`. | N/A |
| DID/DDI Name | A label for the DID/DDI. | Optional | Up to 127 characters. | N/A |
| Force Selected DOD in From Header | Whether to ignore the trunk's From User Part setting and force the extension's chosen DOD number into the `From` header when a user [selects a specific DOD](/pbx/administrator-guide/allow-users-to-select-outbound-caller-id-dod-to-call/) for an outbound call. | Optional | `0` (disabled) or `1` (enabled). | `1` |
| Return 302 on External Forward | Whether to return a `302 Moved Temporarily` response when an inbound call is forwarded to an external number, letting the carrier redirect the call itself. | Optional | `0` (disabled) or `1` (enabled). | `0` |