> Source: [sk94984](https://support.checkpoint.com/results/sk/sk94984)

# sk94984 - VPN traffic is dropped with "Encryption failure: Warning: possible replay attack" log

| Property | Value |
|----------|-------|
| Solution ID | sk94984 |
| Date Created | 2013-10-16 |
| Last Modified | 2024-09-28 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R81.20, R81.10 (EOS), R81 (EOS) |

## Symptoms

- * Site-to-Site VPN traffic is dropped with "*Encryption failure: Warning: possible replay attack*" log.
* An Identity Awareness Policy Decision Point (PDP) Gateway and Policy Enforcement Point (PEP) Gateway have Identity Sharing enabled. The PDP and PEP send Identity Sharing traffic through the VPN tunnel.
* The PDP Security Gateway or the PEP Security Gateway is a cluster. A standby cluster member sends Identity Sharing connections through the VPN tunnel.
* Output of `# fw ctl zdebug + drop` on a VPN Gateway shows:

  ```
  dropped by vpn_ipsec_decrypt Reason: decryption failure: Replay attack;
  ```

## Cause

Identity Sharing is not compatible with VPN configurations when either the PDP Gateway or PEP Gateway operates as a cluster.

The PDP Gateway and PEP Gateway already encrypt Identity Sharing traffic, which makes additional VPN encryption redundant.

## Solution

This solution requires authentication. Please log in to view the full solution.

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