This guide will help you troubleshoot your connection with SIP.US by explaining SIP requirements, solutions for common issues, available tools for self-troubleshooting, resources available directly from our Support team to help resolve your issue.
Successfully establishing a SIP connection is not always easy and depends on the complexity of your SIP device, additional equipment, and local network environment. However, you should be able to handle most issues and successfully register your SIP trunk if you are familiar with how to manage your setup. What follows is a comprehensive look at the SIP registration process with SIP.US.
The process of configuring a SIP trunk varies per device and we recommend starting with viewing Device Setup Guides for a list of common SIP devices. If you cannot find your specific device, use the General SIP Device Configuration guide. If you have matched your settings to the guide and are still having issues with your SIP trunk registration, the next step is determine exactly where you ran into issues during the process.
First, check your SIP trunk registration status in the SIP.US customer portal. You may refer to the guide Check SIP Trunk Registration Status if you are unsure how to do so.
Troubleshooting When "NOT REGISTERED"
If your SIP trunk still does not show as registered in the SIP.US customer portal despite your best efforts, one of two scenarios is happening. The first scenario is that your SIP REGISTER packets are not reaching our gateways. The second scenario is that we are successfully receiving your SIP REGISTER packets, but we are rejecting the registration.
Scenario 1
The first thing that needs to be determined is if the REGISTER packet actually reaches SIP.US. You can register to either of our gateways (gw4.sip.us or gw5.sip.us), but you need to ensure your network allows the REGISTER packet out and that your DNS successfully resolves our gateway IPs. Review the article on Interconnecting with SIP.US to ensure your network security/firewall allows you to connect to our SIP gateways.
Next, reach out to our Support team to determine if your registration attempts are received by SIP.US. We require your public IP and registration attempts with time stamps (from within the past 24 hours) to filter for your register traffic. If we confirm that we are not able to find your register attempts, you will need to go back and assess your equipment and network configuration to find out why.
You should address the following conditions during your troubleshooting:
- Confirm whether or not you received any response from SIP.US regarding your registration request. If yes, move to Scenario 2.
- Is the SIP device actually sending the REGISTER packet? Confirm via a PCAP.
- Have you tried rebooting all of your equipment? Some devices require reboots for settings changes to take effect.
- Did you provide SIP.US with the correct public IP to check for traffic?
- Can you see a REGISTER packet leaving your network via a PCAP? Does the REGISTER packet make it past the firewall?
- What firewalls and network security are in place? Is there any possible security solution you are unaware of? Does the ISP provide equipment that may inspect/block traffic?
- Is there a possible DNS issue? Can you successfully ping one of the SIP.US gateways?
- Can you register your SIP device on a separate network, such as another office location or at home? This can help to isolate your troubleshooting to your network configuration.
Scenario 2
If SIP.US is receiving your REGISTER packet, we should return a SIP code response. Check if you're receiving any specific errors back. Common SIP responses include a 200 OK (for successful registrations), a 401 UNAUTHORIZED for a credential challenge, a 403 FORBIDDEN for incorrect credentials or improperly formatted headers or a banned IP for too many registration attempts, a 407 PROXY IDENTIFICATION REQUIRED if the SIP trunk is configured with IP Auth and the wrong IP/port is used, etc.
You will need to check the format of the headers in your REGISTER packet in most cases to resolve any errors sent back. SIP.US requires several key headers to be formatted in specific formats. Otherwise, we may 401 or 403 the REGISTER packet request. Please note the following:
FROM: This header requires your SIP trunk number directed at a SIP.US gateway FQDN.
Example - 123456789@gw4.sip.us
TO: This header also requires your SIP trunk number directed at a SIP.US gateway FQDN.
Example - 123456789@gw4.sip.us
CONTACT: This header requires your SIP trunk number directed at your public IP and the contact port you assign.
Example - 123456789@63.247.69.226:5060
AUTHORIZATION: This header requires the SIP gateway info, SIP trunk number, and the password.
Example - Digest username="123456789" realm= "gw4.sip.us" password="encrypted string".
Common issues we see include with REGISTER packet headers include:
- FROM and TO headers do not contain the SIP trunk number. Sometimes clients incorrectly put their CID in this field or a random character string.
- FROM and TO headers are not directed at a SIP.US gateway FQDN. Usually we see the client incorrectly use their own IP address or an IP for one of their servers.
- AUTHORIZATION header is missing entirely.
A standard registration communication typically consists of the SIP device sending a REGISTER packet, SIP.US sending a 401 credential challenge, and the SIP device responding with a new REGISTER packet containing the AUTH header, which SIP.US then registers and responds with a 200 OK confirmation status.
This missing AUTH header may be due to the firewall or packet inspection software within the client's network stripping the header before it leaves the local network (the AUTH header may be automatically interpreted as security risk by the software).
- AUTHORIZATION header does not contain all necessary credential information. Same as before, the firewall or network security solution could be automatically removing something, or simply the SIP device is not correctly configured.
- There is a typo in the SIP trunk number, the SIP.US gateway contains a typo, or the password is incorrect.
Our Support team can assist with inspecting your REGISTER packet headers to look for possible errors. Additionally, we can check our IP Blacklist in the event your system has delivered too many failed REGISTER requests and has been temporarily banned. Additionally, we can ensure your traffic originates from the correct public IP address.
Troubleshooting When "REGISTERED"
If you are able to successfully register your SIP device and see the active registration, but issues remain, please review the following common issues and guidance.
Most issues that users encounter tend to manifest in the registration status details:
Note: If you need to register your SIP trunk again with updated changes, you can remove an active registration at any time by clicking "remove registration" as pictured in the screenshot above.
Problem: Inbound calls are failing and/or there is missing audio.
Contact Address Doesn't Match Source Address
Note the line below “REGISTRATION STATUS.” If you have successfully registered your PBX/Phone with our service you should see a string like this (the string is edited out of the image above for privacy/security):
sip:Trunk#@<YOUR CONTACT IP>:<YOUR PORT>;alias:<YOUR SOURCE IP>:<YOUR PORT>
Example: sip:123456789@142.93.###.###:5060; alias=142.93.###.###:5060
The key thing to confirm is that both strings match the same IP and port combinations. This is because the first IP in the registration string reads from the CONTACT header of the SIP REGISTER packet sent to SIP.US. The second IP in the registration string displays the public IP from which the REGISTER packet originated.
The CONTACT header is user-defined in the SIP device, so SIP.US displays what it receives and this is how the two IPs can potentially conflict. SIP.US attempts to deliver inbound traffic to the IP defined in the CONTACT header. If your system does not receive inbound calls and there is an IP conflict, that can serve as an indicator of where to look in your configuration to apply the necessary changes.
There are a number of things which can cause IP conflicts, including user error in the manual configuration, a power outage affecting a non-static IP (in which your ISP changes your public IP address but the SIP device does not detect the change), a custom-implemented NAT policy, or a firewall/security solution automatically applying NAT changes you're not aware of.
Security/Firewall-related Issues
Port conflicts in the registration are also common with NAT policies and firewall port remapping. Most PBX systems use port 5060 by default. If the port is some funky number like 49784, chances are that your firewall/router is doing Port Address Translation (PAT). This doesn't always mean your calls won't work, but calls may not work intermittently (the cause of the intermittent issue is beyond the scope of this article). The best solution is to use 1:1 port translation so that your port does not change through translation.
SIP.US cannot help with troubleshooting a firewall, so you will need to reach out to the vendor in these scenarios. However, our Support team can assist in providing information such as what IPs and ports we see SIP responses from to assist in your troubleshooting.
Note: If you have proper port forwarding in place, your system can function properly. This is all outside of the realm of support for SIP.US though.
Contact Address is a Private IP Instead of Public IP
Inspect the IP address and port very carefully in the SIP register string. If the first IP address displayed falls within the following IP ranges, we will be unable to deliver your calls:
10.0.0.0 – 10.255.255.255
172.16.0.0 – 172.31.255.255
192.168.0.0 – 192.168.255.255
These are private IP addresses which are used within your Local Area Network (LAN). Private IP addresses are not routable on the internet. Your ISP gives you/your router a public IP address which is not in those ranges. That public IP address is the one that needs to be in the string. To find your public IP address, simply query a search engine “What is my IP.” Your public IP should be returned as the top result. There are also many free lookup tools available that will appear in the same search results.
If you cannot seem to get your public IP and port combination to show up in the string, you may want to use a STUN server. Within most phones/PBX systems there is a field to input a STUN server. You may use ours by putting in “stun.sip.us” in the field for “STUN Server” on your system and use port 3478.
Problem: Registration keeps dropping.
UDP Timeout in Firewall
Some users notice their registration drops on a routine interval. This can sometimes be attributed to the UDP timeout value in the firewall. Try setting the UDP timeout value to match or exceed the registration interval for the SIP device. Additional changes in the firewall may be required, in which we recommend reaching out to the firewall vendor for support.
Network Reliability Issue
Another common scenario in which registration regularly drops is attributable to the overall reliability of your network connection to SIP.US. If you notice your registration regularly drops, but there is no pattern to the behavior, packet loss or excess latency may be the cause. These issues can sometimes be difficult to pinpoint and you will need to run tests throughout your network to try and pinpoint the root issue.
- A packet loss test will check the general reliability of your network (you can reach out to the ISP directly or find multiple free options via search engine results). Open a support ticket with the ISP to rule out any packet loss on their end when attempting to establish a connection with SIP.US.
- Check your network and equipment for any high hardware or network utilization that may be affecting the quality of your connection and consider implementing a Quality of Service (QoS) policy, also known as traffic shaping.
- Inspect the router, switches, and cables to your phone system for any signs of damage or degradation. Try alternate equipment configurations to see if there is any indication of a point of failure.
Problem: Device is no longer registered but registration shows active in portal.
Device Registration Interval
Registration intervals are defined in seconds, and some devices may use high default value for the registration interval. The problem with this is that if the connection drops between your equipment and SIP.US, your SIP device won't try to register again until it reaches that next interval refresh. As an example, some devices may use a default value as high as 3600 seconds (1 hour). SIP.US recommends using a value of 60 or 120 seconds. You can also see in the screenshot below where to see the expiry time for the current registration in the customer portal.
Problem: Registration details appear correct and there are no registration drops, but inbound and/or outbound calls fail.
Call Routing Issue
The issue is likely not related to registration. Suspect possible configuration issues with inbound routing and refer to our Device Setup Guides. Additionally, check these articles on Inbound Calls are Failing and Setting up Outbound Calling.
Please feel free to open a ticket with Support at support@sip.us if you are still having issues and require further assistance.