How to Interconnect Branches for Yeastar PABX Through Port Forwarding Leave a comment

Businesses with multiple offices often need their branches to communicate seamlessly without paying for every inter-office call. Yeastar PABX inter-branch connectivity makes it possible to connect offices over the internet so users can call extensions at another branch as if they were on the same telephone system.

One practical way to achieve this is by using port forwarding on the internet routers at each branch. This guide explains how to connect Yeastar P-Series PABX systems between branches using public IP addresses and SIP peer trunks.

What Is Yeastar Inter-Branch Connectivity?

Yeastar inter-branch connectivity allows two or more Yeastar PABX systems installed at different physical locations to communicate with each other over an IP network.

For example:

• Head Office: Yeastar PABX – Nairobi
• Branch 1: Yeastar PABX – Mombasa
• Branch 2: Yeastar PABX – Kisumu

Users at Head Office can dial an extension at Mombasa or Kisumu without making a conventional external telephone call.

A typical setup looks like this:

Head Office Yeastar PABX → Internet → Branch Yeastar PABX

Port forwarding allows SIP traffic arriving at a branch’s public IP address to be forwarded to the Yeastar PABX on its private LAN address.

Benefits of Connecting Yeastar PABX Branches

Interconnecting your Yeastar systems can provide several benefits:

• Free internal calls between branches
• Extension-to-extension dialing between offices
• Centralized call management
• Reduced communication costs
• Easier communication between departments
• Ability to transfer calls between branches
• Scalability for additional offices
• Integration of remote offices into one business telephone environment

What You Need Before Starting

For a reliable setup, each branch should have:

1. A Yeastar PABX.
2. A stable internet connection.
3. A router/firewall that supports port forwarding.
4. A static public IP address, preferably.
5. A fixed private IP address for the Yeastar PABX.
6. Administrator access to the Yeastar PABX.
7. Administrator access to the branch router.

Static Public IP vs Dynamic IP

A static public IP is strongly recommended because the PABX needs to remain reachable from the other branch.

If your ISP provides a dynamic public IP, you can consider using a DDNS service, provided your Yeastar and network configuration support it.

Step 1: Give Each Yeastar PABX a Static LAN IP

First, make sure each Yeastar PABX has a fixed IP address on its local network.

For example:

Location	Yeastar IP	Public IP
Head Office	192.168.1.10	41.x.x.x
Branch 1	192.168.2.10	102.x.x.x
Branch 2	192.168.3.10	105.x.x.x

The actual IP addresses will depend on your network.

Avoid allowing the PABX’s LAN IP to change because this can cause port-forwarding rules to stop working.

Step 2: Configure Port Forwarding

Log into the router at the branch where the Yeastar PABX is installed.

Look for a menu such as:

NAT → Port Forwarding

or:

Virtual Server → Port Forwarding

Create rules forwarding the required Yeastar services from the router’s public interface to the internal Yeastar PABX IP address.

For example:

Port	Protocol	Purpose
5060	UDP/TCP	SIP signaling, depending on configuration
RTP range	UDP	Voice/audio traffic
HTTPS management port	TCP	Web access, if remote management is required

Important: Do not blindly expose every Yeastar service to the internet. The exact SIP and RTP ports depend on your Yeastar model and configuration. Check the Yeastar documentation and the ports configured under the PABX’s SIP/RTP settings.

For security, it is preferable to restrict source IP addresses where possible.

Step 3: Configure NAT and SIP Settings

Port forwarding alone is not always sufficient for VoIP.

The Yeastar PABX must correctly advertise its public address when communicating with the remote PABX.

Check the Yeastar network/SIP settings for options relating to:

• NAT
• External IP address
• Local network identification
• SIP transport
• RTP port range

Make sure the external/public IP address is correctly configured where required.

Incorrect NAT settings can result in situations where:

• Calls connect but there is no audio.
• Audio works in one direction only.
• Calls disconnect after a few seconds.
• Extensions cannot register.

Step 4: Create a Peer Trunk Between the PABXs

Once the network and port forwarding are working, create a trunk between the two Yeastar systems.

For example:

Head Office → Branch 1

On the Head Office Yeastar PABX, create a peer/SIP trunk pointing to the Branch 1 public IP address.

The configuration will generally include:

• Trunk name
• Remote host/public IP
• SIP port
• Transport protocol
• Authentication, where applicable
• Outbound routing

The exact menu names vary depending on the Yeastar P-Series firmware version.

Repeat the process in the opposite direction if your design requires bidirectional peer connectivity.

Step 5: Create Outbound Routes

After creating the trunk, tell the Head Office PABX which numbers should be sent to the branch.

For example, you could allocate:

• Head Office extensions: 1XX
• Branch 1 extensions: 2XX
• Branch 2 extensions: 3XX

A user at Head Office could then dial:

201 → Branch 1

while a Branch 1 user could dial:

101 → Head Office

The outbound routes determine which calls are sent through the inter-branch trunk.

Step 6: Configure Inbound Routes

The receiving PABX also needs to know what to do with calls arriving from the other branch.

Create appropriate inbound routes so calls coming through the inter-branch trunk are delivered to the correct extension, department, ring group or IVR.

For example:

Head Office → Branch 1 → Extension 201

The Branch 1 PABX receives the SIP call and routes it to extension 201.

Step 7: Test Inter-Branch Calling

Once both systems are configured, test the connection.

Try:

1. Head Office extension → Branch extension.
2. Branch extension → Head Office extension.
3. Two-way voice communication.
4. Call transfer between branches.
5. Hold and resume.
6. Caller ID.
7. Ring groups, if required.

If the call connects but there is no audio, investigate the RTP/NAT configuration first.

Common Yeastar Inter-Branch Problems

1. Calls Do Not Connect

Check:

• Public IP addresses
• Port forwarding
• SIP port
• Firewall rules
• Trunk configuration
• SIP authentication
• Whether the ISP is using CGNAT

2. Call Connects but There Is No Audio

This is usually related to RTP or NAT configuration.

Check:

• RTP port range
• RTP port forwarding
• Yeastar external IP/NAT settings
• Firewall rules
• Router SIP ALG

3. Audio Works Only One Way

This is another common NAT problem.

Check the RTP path in both directions and make sure the routers are not blocking UDP traffic.

4. Public IP Does Not Work

Your ISP may be using Carrier-Grade NAT (CGNAT).

In this situation, normal port forwarding on your router may not make the PABX accessible from the internet.

Ask your ISP for a public/static IPv4 address.

5. SIP ALG Causes Problems

Some routers have SIP ALG enabled. SIP ALG can modify VoIP packets and sometimes interfere with Yeastar SIP communication.

If you experience strange registration, call connection or audio problems, check whether SIP ALG can be disabled on the router.

Security Considerations

Exposing a PABX directly to the internet requires careful security configuration.

Never use simple SIP passwords or expose unnecessary services.

Recommended measures include:

• Use strong SIP passwords.
• Keep Yeastar firmware updated.
• Restrict allowed source IP addresses where possible.
• Forward only required ports.
• Avoid exposing the PABX web interface unnecessarily.
• Use firewall rules.
• Monitor SIP registration and call activity.
• Disable unused accounts and services.
• Consider VPN-based connectivity for higher security.

Is Port Forwarding the Best Way to Connect Yeastar Branches?

Port forwarding can work well, especially for businesses that have static public IP addresses and properly configured firewalls.

However, for a business environment, a site-to-site VPN can often provide a more secure architecture because the PABXs communicate through a private network rather than exposing SIP services directly to the internet.

For example:

Head Office LAN → VPN Tunnel → Branch LAN

With a VPN, the Yeastar systems can communicate using their private IP addresses, reducing the need to expose SIP services publicly.

The best solution depends on the company’s network architecture, internet connections, security requirements and number of branches.

Yeastar PABX Inter-Branch Installation in Kenya

If your company operates multiple offices in Nairobi, Westlands, Mombasa, Kisumu or other parts of Kenya, Yeastar PABX inter-branch connectivity can provide a cost-effective way to link your telephone systems.

A professional installation can include:

• Yeastar PABX supply and installation
• Inter-branch SIP trunk configuration
• Router and firewall configuration
• Port forwarding
• Site-to-site VPN
• Extension planning
• Call routing
• Remote troubleshooting
• Yeastar P-Series configuration
• Ongoing PABX maintenance and support

Conclusion

Interconnecting Yeastar PABX branches through port forwarding allows businesses to establish communication between offices over the internet. By assigning static LAN addresses, configuring NAT and port forwarding, creating SIP peer trunks, and setting appropriate inbound and outbound routes, users can make extension-to-extension calls between branches.

For improved security, businesses should also consider VPN-based Yeastar inter-branch connectivity, particularly when several offices are involved.

If you need professional Yeastar PABX installation, inter-branch configuration, SIP trunking, networking or VoIP support in Kenya, working with an experienced Yeastar installer can help ensure that both the voice and network infrastructure are configured correctly.

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