> Source: [sk185119](https://support.checkpoint.com/results/sk/sk185119)

# sk185119 - IPv6 Default Gateway Disappears on Windows Clients Behind ElasticXL or Scalable Platform Gateways

| Property | Value |
|----------|-------|
| Solution ID | sk185119 |
| Date Created | 2026-07-02 |
| Last Modified | 2026-09-10 |
| Technical Level | Advanced |
| Products | Scalable Platforms |
| Versions | R82.10, R82 |
| OS | Gaia |
| Platform | OCI |

## Symptoms

- * After replacing a Security Gateway with an ElasticXL cluster, Windows 11 clients do not retain the IPv6 default gateway on VLAN interfaces.
* Windows removes the IPv6 default route from its routing table shortly after the clients learn the IPv6 default gateway.
* Clients can access the internet over IPv6 for only a short time. IPv6 connectivity then fails when the IPv6 default gateway disappears.
* The issue was observed in multiple environments, including ElasticXL sites and Maestro / Scalable Platform sites.

## Cause

* On ElasticXL and Scalable Platform Security Gateways, IPv6 Neighbor Advertisement traffic can affect the client default router state.
* The Security Gateway sends unsolicited IPv6 Neighbor Advertisement packets to the all-nodes multicast address **ff02::1** approximately every 60 seconds. These Neighbor Advertisement packets have the Router flag set to **0**.
* When a Windows host receives a Neighbor Advertisement for a router and detects that the Router flag changed from **1** to **0**, the host removes that neighbor from its Default Router list. As a result, Windows deletes the IPv6 default route that it previously learned from SLAAC and Router Advertisements.

## Solution

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