> Source: [sk184386](https://support.checkpoint.com/results/sk/sk184386)

# sk184386 - GRE tunnel to a non-Check Point peer drops packets

| Property | Value |
|----------|-------|
| Solution ID | sk184386 |
| Date Created | 2025-12-08 |
| Last Modified | 2026-01-07 |
| Technical Level | Advanced |
| Products | Security Gateway, Scalable Platforms |
| Versions | R82, R81.20, R81.10 (EOS), R82 |
| OS | Gaia |

## Symptoms

- * GRE tunnel to a non-Check Point peer drops packets.

  Additional Observations:
  * No duplicate IP addresses are observed.
  * Traffic capture shows packets returning with the Security Gateway's own GRE interface IP as the source.
  * The Anti-Spoofing mechanism drops these packets.

  <br />

  <br />

* The follow drop was observed with a specific interval like 10 seconds while running "fw ctl zdebug + drop \| grep gre_remote_ip".  

  `@;6084163.338;[cpu_1];[SIM4];sim_pkt_send_drop_notification: (0,0) received drop, reason: Local Spoofing (12), conn: `;

## Cause

The peer device establishes a GRE tunnel with Keepalive enabled. Check Point Security Gateways do not support GRE Keepalive. When Keepalive packets return with the Security Gateway's IP as the source, the Anti-Spoofing mechanism identifies them as spoofed and drops them.

## Solution

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