SIPTRUNK offers the PSTN Forward in the event you need to route all call traffic to an external phone number (such as a cell phone) and wish to bypass your phone system and all other Call Failover Options entirely. This feature is useful if you’re having issues with your phone system, such as an outage, or need to immediately redirect all call traffic to a new receiving party.
Note: Call forwarding occupies two concurrent channels; one for the inbound leg and one for the outbound leg. Your SIP trunk needs at least two channels for a forward to work.
Setting a PSTN Forward in the Customer Portal
Hover of the “SIP Trunking” menu tab and choose the “Phone Numbers” submenu option. The page will load a list of all DIDs on the account. Click on the pencil edit icon next to the DID you wish to place the forward on and then fill out the “PSTN Forward” field with the phone number you wish to forward out to. Be sure to click “Submit” to apply the changes.
It is important that you format the forward with a 1 at the beginning if you are forwarding to a North American number.
Example: 18005669810 (broken up for readability: 1-800-566-9810)
You may also forward to an international number, but your SIP trunk will need to be configured for international calling. Add the country code of the international destination at the beginning of the input number.
Example (UK number): 442039911100 (broken up for readability: 44-203-991-1100)
Call Forwards in CDRs
As noted above in the article, all call forwarding requires two concurrent active channels. When a forward happens, the call routes inbound and identifies the forwarding rule and then SIPTRUNK automatically sends the call back out to the defined destination. For this reason, you will see all call forwards appear in the Call Detail Records (CDRs) as two separate calls, but with equivalent start time and duration timestamps.
Note: SIPTRUNK will pass the originating CID for PSTN Forwards, but be aware that if a user previously set a universal CID Override in the SIP trunk settings, it will still affect the caller ID on the outbound leg.
Requirements for Call Forwarding
Due to the nature of call forwarding, there will always be both an inbound leg and an outbound leg for all related call traffic. Therefore, it is necessary for your SIP trunk to have a minimum channel capacity of two in order for the forward to work.
If you have an Unlimited Calling Rate Plan, you need to have at least two channels plus additional capacity for any other traffic expected to pass through the SIP trunk at the same time. If you exceed the maximum channel capacity, or channel limit, all of those calls will fail until active calls are ended and the capacity free up again.
If you pay for a monthly minutes package, you have access to unlimited channels (you can use the minutes whenever you want). The default channel capacity on a SIP trunk with a minutes package is 24 channels. You may request Support to modify this value if needed.
Note: These forwarding requirements also apply to PSTN Backups and any forwarding you handle at the PBX/phone system level.
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