---
title: "CT Cloud SIP - Trunk Info and Requirements"
slug: "ct-cloud-sip-trunk-info-and-requirements"
updated: 2026-09-18T16:23:29Z
published: 2026-09-18T16:23:29Z
canonical: "learn.calltower.com/ct-cloud-sip-trunk-info-and-requirements"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://learn.calltower.com/llms.txt
> Use this file to discover all available pages before exploring further.

# CT Cloud SIP - Trunk Info and Requirements

## Requirements

CallTower requires that customer's PBX support the following:

Codec: G.711ulaw and G.729

Port/protocol: UDP 5060

DTMF: RFC2833

RTP (audio) ports: 16384 - 65535

> [!CAUTION]
> *CallTower is not responsible for configuration of customer equipment, including firewall and PBX*

## Digest Auth Trunks

Please ensure that adjustments are made to your firewall to trust all traffic that is sourcing from the following IP addresses for signaling and media:

205.196.170.135

205.196.171.135

Configure your PBX to register using DNS SRV record telephonenumber.sipservice.appiaservices.com (i.e. 7009912345.sipservice.appiaservices.com), where telephonenumber is the telephone number of the PBX provided to you by CallTower. If your PBX doesn't support DNS SRV records, then use one of the following and please advise CallTower, so we can update your trunk configuration accordingly:

**Primary:** [telephonenumber.sipservice1.appiaservices.com](http://telephonenumber.sipservice1.appiaservices.com) --> 205.196.170.135

**Secondary**: [telephonenumber.sipservice2.appiaservices.com](http://telephonenumber.sipservice2.appiaservices.com) --> 205.196.171.135

## IP Auth Trunks

Please ensure that adjustments are made to your firewall to trust all traffic that is sourcing from the following IP addresses for signaling and media:

205.196.170.136

205.196.171.136

Configure your PBX to use DNS SRV record ipauth.appiaservices.com to configure your PBX, if it supports it. If your PBX doesn't support DNS SRV records, then use one of the following and please advise CallTower, so we can update your trunk configuration accordingly:

**Primary:** ipauth1.appiaservices.com --> 205.196.170.136

**Secondary:** [ipauth2.appiaservices.com](http://ipauth2.appiaservices.com) --> 205.196.171.136