> Source: [sk105697](https://support.checkpoint.com/results/sk/sk105697)

# sk105697 - ClusterXL interfaces are flapping when connected to Cisco Nexus switches

| Property | Value |
|----------|-------|
| Solution ID | sk105697 |
| Date Created | 2015-04-20 |
| Last Modified | 2018-03-01 |
| Technical Level | General |
| Products | Security Gateway |
| Versions | R82.10, R82, R81.20 |

## Symptoms

- * SmartView Tracker logs and output of "*cphaprob -a if*" command show that ClusterXL interfaces change their status between "Down" and "Up" several times a minute (interfaces are flapping).

* ClusterXL interfaces are connected to Cisco Nexus switches.

## Cause

[Cisco Bug: CSCuc98155](https://tools.cisco.com/quickview/bug/CSCuc98155) - MAC Address tables on Cisco Nexus switches are not synchronized when vPC (virtual port channeling) is used.

## Solution

This is not a Check Point issue. Cisco reports that CSCuc98155 is resolved in Cisco NX-OS Release 5.2(1)N1(6).

If you do not update to this release, disable vPC on Cisco Nexus switch.

**Workaround** is to change the CCP mode on all involved cluster members from Multicast to Broadcast as described in [sk20576 - How to set ClusterXL Control Protocol (CCP) in Broadcast / Multicast mode in ClusterXL](http://supportcontent.checkpoint.com/solutions?id=sk20576).

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