Background:

 

This guide offers a comprehensive overview of common VPN problems and their solutions. It focuses on two primary types of issues:
1. Unable to Connect to the VPN Server.
2. Connected to the VPN Server but Lacking Internet or Local Access.

 

This Article Applies to:

 

All TP-Link(Omada) routers.

 

Troubleshooting Steps:

 

Issue 1: Unable to Connect to the VPN Server.

 

1. IP address design and conflicts

It is always wise to check if you have configured your VPN server properly if you export the VPN file from your built VPN server.

Misconfiguring the subnet or the VPN interface IP could cause a VPN connection problem.

 

If your VPN server is a dynamic IP with DDNS or a domain name, please make sure that your DNS server is reachable from your router WAN interface. This matters because the VPN server domain needs to be resolved before a connection is established.

 

Also, avoid any overlapped IP addresses or subnets in any of the networks you are connecting or creating.

 

2. Make sure your time is correct.

As it can cause the TLS connection failure. The accuracy of the time on your local machine is crucial for various types of network connections, including VPN, which rely on bidirectional handshakes. Please verify that your time settings are correctly synced.

 

3. Consider temporarily disabling firewall and security software.

To troubleshoot connectivity issues, try closing any firewall or security software that may be blocking the VPN connection. Remember to re-enable these features once the VPN connection is successfully established.

 

If you are in a business environment where your company may have activity recording and anti-virus software, you may not be able to establish the connection due to them. Please contact your IT department before you make any outbound encrypted connection.

(We are not responsible for any unauthorized use in terms of the VPN establishment. )

 

4. Make sure you are not censored by your country when the VPN server resides in another country.

In some cases, your country's national firewall may block VPN connections when the server is located in a different country or on its blocklist. The distinct signature and traffic patterns of VPNs can be easily detected.
If your VPN server is hosted in a different country, it is advisable to inform your local authorities to avoid potential issues. Test the connection domestically to ensure it is not blocked by national departments. Please note that while encryption is provided, bypassing or masking traffic for censorship purposes is not within our capabilities.

 

Even for domestic VPN connection, it could also be detected by the local authorities because of the VPN traffic pattern. If you try a VPN server fail multiple times, you might wanna check if your ISP blocks the port.

 

If you have checked the port and with ISP, both are green, you should consider contacting technical support regarding the problem you experienced.

 

5. Compatibility.

PPTP VPN is out of date and certain VPNs got their versions like WireGuard and OpenVPN. If the server or the client version is too old or if either end of the server/client software has not caught the latest release of the VPN types mentioned, it could fail to connect due to a different encryption for cipher. In this case, sometimes, you should check if you can make both ends meet each other. Or update the firmware/software if there is a new version.

 

6. Always take a second check on your VPN configurations.

It is also necessary to review your VPN server and client configuration.

Though you might find it unnecessary most of the time, we have witnessed too many cases caused by a simple error in the IP or the letter in the configuration. Take a second and check it again.

 

Issue 2: Connected to the VPN Server but Lacking Internet or Local Access

 

1. ACL check.

Check if your remote VPN server(if it is a router) has an ACL entry that affects the communication.

Review the ACL settings on the remote site client/server if there are any entries stop the unknown IP from accessing it.

 

2. Ping the remote VPN server Default Gateway

From the client side, use the ping command to test connectivity to the remote site default gateway. If you cannot ping the gateway, it may indicate a network or routing issue.

If you can ping to the remote site default gateway, but not to the remote clients, that's usually a firewall issue on that computer/server.

 

3. Disable the Firewall and anti-virus if you are using a computer.

For both ends, it is worth trying temporarily turning off the firewall on the endpoint device (such as routers, switches, or computers) to see if the firewall settings are preventing access to the local network. Add Exception Rules: If disabling the firewall allows access to the local network, it is advisable to add exception rules that allow VPN traffic through the firewall instead of completely turning it off.

 

If disabling the firewall allows access to the local network, it is advisable to add exception rules that allow VPN traffic through the firewall instead of completely turning it off.

 

4. Configuration check.

If you need to use an Internet proxy with your VPN connection, be sure that your server allows that. If it does not allow you to use the proxy mode, then you cannot use its VPN IP address to browse the Internet.

With the correct VPN type(IPsec does not support proxy mode), usually with the full mode on the server, you should be able to get proxied access.

 

5. Packet block due to ISP.

For this, you may Wireshark on your router WAN and refer to the Wireshark guide on our official website FAQ.

For IPsec, if your ESP is blocked by your ISP, you are not permitted to pass traffic between the sites or client-to-site connection even though your connection shows as established. Reach out to your ISP regarding this issue.

(This case means your ISP specifically blocked ESP instead of other AH, IKE, ICMP and UDP. These are unaffected but ESP is blocked, so the status shows as established but not working in actuality.)

 

Other types of VPNs are known and their pattern is clear. If your ISP forces a restriction, DPI, or middle-man attack to examine your traffic, we are not able to resolve this for you but be honest with your ISP and check if any of the protocols is blocked or not allowed by their firewall.

 

Note:

 

1. As IPv4 drains today, the ISP may charge you for the public IPv4 address. Please address this issue on your end or you can NOT use the VPN service.
2. For the CG-NAT ISP, you can NOT use the VPN or port forwarding and affect the NAT Type. You can contact the ISP and ask them to offer a Statis IP address if they can provide one.

3. If you don't have a static IP address but a dynamic IP address on your WAN interface, please make sure you have configured the DDNS. DDNS provider may charge you for the domain name you are going to bind. Please proceed at your discretion.

4. ISPs can stop your traffic based on their policy. See the case for sudden VPN disconnections after a while.

 

Update Log:

 

Dec 4th, 2024:

Update this guide.

 

Oct 21, 2024:

Release of this article.

 

Recommended Threads:

 

No Traffic After OpenVPN Is Connected - Android/iOS OpenVPN Connect 3.4.0 Update

How to Configure Site-to-Site WireGuard VPN on Omada Controller

How to Configure GRE VPN on Omada Router

 

Feedback:

 

• If this was helpful, welcome to give us Kudos by clicking the upward triangle below.
• If there is anything unclear in this solution post, please feel free to comment below.

 

Thank you in advance for your valuable feedback!

 

------------------------------------------------------------------------------------------------

Have other off-topic issues to report? 

Welcome to > Start a New Thread < and elaborate on the issue for assistance.