> Source: [sk181356](https://support.checkpoint.com/results/sk/sk181356)

# sk181356 - Client connection to the Site VPN cannot be established when the"/31" prefix is used on the Internet connection

| Property | Value |
|----------|-------|
| Solution ID | sk181356 |
| Date Created | 2023-08-03 |
| Last Modified | 2025-12-22 |
| Technical Level | General |
| Products | Security Gateway |
| Versions | R82, R81.20, R81.10 (EOS), R81 (EOS) |
| OS | Gaia |

## Symptoms

- * There is no access to the site via Remote access VPN. And creating a new VPN site fails with the "*Remote Access, Site is not responding. You might be in a hotspot environment.*" error. The Security Gateway does not respond to the client.
* The issue occurs if the VPN Gateway uses the "*/31*" subnet mask on the external link or link selection interface.
* TCPDUMP shows that traffic arrives at the Security Gateway but the Gateway does not respond.

## Cause

According to RFC 3021, 31-Bit Prefixes on IPv4 are for Point-to-Point Links.

## Solution

[Contact Check Point Support](https://www.checkpoint.com/support-services/contact-support/) to get a Hotfix for this issue.

A Support Engineer will make sure the Hotfix is compatible with your environment before providing it.  
For faster resolution and verification, collect these files:

1. [CPinfo](https://support.checkpoint.com/results/sk/sk92739) file from the Management Server involved in the case.
2. [CPinfo](https://support.checkpoint.com/results/sk/sk92739) file from the Security Gateway / each Cluster Member involved in the case.

**Hotfix installation instructions:**   
Refer to [sk168597 - How to install a Hotfix](https://support.checkpoint.com/results/sk/sk168597).

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