> Source: [sk168076](https://support.checkpoint.com/results/sk/sk168076)

# sk168076 - Port switch is flapping, Cluster Members have similar MAC addresses 

| Property | Value |
|----------|-------|
| Solution ID | sk168076 |
| Date Created | 2020-07-16 |
| Last Modified | 2021-11-10 |
| Technical Level | General |
| Products | Security Gateway |
| Versions | R82.10, R82, R81.20 |

## Symptoms

- * A port switch is flapping in a Cluster XL configuration.

* In the same network segment, different cluster members have similar MAC addresses. Example - `02:00:00:00:00:00` and `02:00:00:00:00:01`

## Cause

Cluster Members with the fixed source MAC address `02:00:00:00:00:mem_id` are forwarding cluster correction packets.

When you run more then one cluster in the same segment ([sk25977](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk25977&partition=Basic&product=ClusterXL,)), port flapping can occur because two different Cluster Members have the same correction MAC address.  

For example:   
`02:00:00:00:00:00` - The correction packets from member 1 (on both clusters)  
`02:00:00:00:00:01` - The correction packets from member 2 (on both clusters)

## Solution

This problem was fixed. The fix is included starting from:

* [Check Point R81](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk166715)
* [Jumbo Hotfix Accumulator for R80.40](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk165456) starting from Take 100 (Hotfix is off by default, see installation instructions below)
* [Jumbo Hotfix Accumulator for R80.30](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk153152) starting from Take 237 (Hotfix is off by default, see installation instructions below)
* [Jumbo Hotfix Accumulator for R80.20](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk137592) starting from Take 190 (Hotfix is off by default, see installation instructions below)

Check Point recommends to always upgrade to the most recent version ([Security Gateway](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doShowproductpage&productTab=downloads&product=435) / [VSX](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doShowproductpage&productTab=downloads&product=359) / [Security Management Server](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doShowproductpage&productTab=downloads&product=184) / [Multi-Domain Security Management Server](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doShowproductpage&productTab=downloads&product=166) / [SmartConsole](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doShowproductpage&productTab=downloads&product=191)).  

The solution is to add the *cluster_id* to the correction MAC. This value is unique for each Cluster Member `02:xx:xx:00:00:yy`.  

xx - Cluster ID  
yy - Member ID  

**Note:** During Hotfix installation, when one Cluster Member has the Hotfix installed and the other does not, traffic originated from the standby member fails This issue is resolved once both Cluster Members has the fix installed.  

**Hotfix Installation Instructions**To enable the Hotfix, follow this procedure on each Cluster Member:

1. Connect to the command line.
2. Log in to the Expert mode.
3. In the CLI, enter this command : `fw ctl set int ccl_use_cluster_id_mac 1 --a`
4. Edit the *$FWDIR/boot/modules/fwkern.conf* file:   
   ` [Expert@HostName:0]# vi $FWDIR/boot/modules/fwkern.conf`  
   **Note:** If this file does not exist, then create it.
5. Add this line (spaces and comments are not allowed):  
   `ccl_use_cluster_id_mac=1`
6. Save the changes in the file and exit the Vi editor.
7. Edit the $PPKDIR/conf/simkern.conf file:   
   \[Expert@HostName:0\]# vi $PPKDIR/conf/simkern.conf  
   **Note:**If this file does not exist, then create it.
8. Add this line (spaces and comments are not allowed):   
   `ccl_use_cluster_id_mac=1`
9. Save the changes in the file and exit the Vi editor.

**Hotfix installation instructions:**   
Refer to [sk168597 - How to install a Hotfix](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk168597).

**Related solutions:**

* [sk25977 - Connecting multiple clusters to the same network segment (same VLAN, same switch)](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk25977)
* [sk167874 - Traffic originated by the Standby cluster member does not work during upgrade to R80.40 Jumbo HFA](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk167874)

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