> Source: [sk180956](https://support.checkpoint.com/results/sk/sk180956)

# sk180956 - Traffic through a VPN tunnel does not flow as expected when "Link Selection probing" and "NAT Traversal" are enabled.

| Property | Value |
|----------|-------|
| Solution ID | sk180956 |
| Date Created | 2023-05-17 |
| Last Modified | 2026-07-22 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R82.10, R82, R81.20, R81.10 (EOS), R81 (EOS) |

## Symptoms

- * Traffic through a VPN tunnel does not flow as expected when "Link Selection probing" and "NAT Traversal" are enabled.
* The VPN Gateway forwards traffic upstream on port 500 using a MAC address. However, NAT traversal (NAT-T), uses port 4500 and a different MAC address. The MAC address used by NAT-T does not exist upstream of the VPN Gateway.
* Clearing the `orig_route_params` on the VPN Gateway / all Cluster members with: `# fw tab -t orig_route_params -x -y` does not resolve the issue.

## Solution

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