Skip to main content
507adminJ
507adminJ
New Member
September 8, 2025
Question

Infrastructure migration to FortiSwtich: issues with VOIP

  • September 8, 2025
  • 3 replies
  • 710 views

I'm a fairly green network admin, but I am trying to migrate from old switches to new FortiSwitches that we recently purchased. The old switches are a mixture of HPE switches and the FortiSwitches are all 124F-FPOE and 148F-FPOE with a 1024E as the core managed by a FortiGate 201F via FortiLink.

 

Unfortunately, the Fortigate is not the primary L3 device for most of our main VLANS. Therefore, I am trying to extend VLANS from the old switches to the new switches via a trunk port between the new FS-1024E and the old HPE core. Before I made a physical connection between the core switches, I attempted to create software switches on the FG that had two interfaces as members. One interface was a VLAN on a physical port connected to the old core and the other interface was a VLAN on FortiLink. Both VLAN interfaces had the same VLAN IDs and no IP info as the gateway exists on an aging Sophos device.

 

I created one of these software switch bridges for a small VLAN and it seemed to work, so I then created another one for our VOIP VLAN. I put the IP phone at my desk onto the VOIP VLAN and it booted with my name and extension on the display as normal so I thought I was in business. Shortly after this (15 minutes or so maybe) a tier one tech came in and asked me if the internet was down... and it was. Rather the interfaces that connect our FG to our ISPs were down. I was already tooling around on the FG gui and when I went to Network > Interfaces I was met with a red box at the top of the page that the device was operating in conserve mode. I really wasn't sure what to do, so I quickly just disabled the software switches that I had created and in a few minutes things went back to normal.

 

I am now trying to use a physical connection between the two core switches as I mentioned previously instead of software switches on the FG, but I am scared to try again because I don't want to take down our whole network. I apologize for turning this into "story time", but I am not entirely sure where my problem lies. I am trying to give an overview of my situation rather than ask something like "How do I configure VOIP on Fortinet gear?" in case the duct-tape and popsicle sticks nature of my set up is the larger issue.

 

Thank you in advance for any assistance that you're willing to provide.

3 replies

Jean-Philippe_P
Staff & Editor
Jean-Philippe_P
Staff & Editor
September 11, 2025

Hello 507adminJ, 

 

Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible. 

 

Thanks, 

Jean-Philippe - Fortinet Community Team
Jean-Philippe_P
Staff & Editor
Jean-Philippe_P
Staff & Editor
September 12, 2025

Hello,

 

We are still looking for an answer to your question.

 

We will come back to you ASAP.

 

Thanks,

Jean-Philippe - Fortinet Community Team
Jean-Philippe_P
Staff & Editor
Jean-Philippe_P
Staff & Editor
September 15, 2025

Hello 507adminJ,

 

I found this solution. Can you tell us if it helps, please.

 

It seems like you're dealing with a complex network migration scenario. Here are some steps and considerations to help you proceed safely:

 

  1. Understand Conserve Mode: Conserve mode is triggered when the FortiGate's memory usage exceeds a certain threshold. This can happen due to high traffic or resource-intensive configurations. Disabling the software switches likely reduced the load, bringing the device out of conserve mode.

  2. Review Software Switch Configuration: Ensure that the software switches are configured correctly. Misconfigurations can lead to loops or excessive traffic, causing high resource usage.

  3. Use Physical Connections: Establish a physical trunk link between the FortiSwitch and the HPE core switch. This is generally more stable and less resource-intensive than using software switches on the FortiGate.

  4. Configure VLANs Properly: Ensure that VLANs are consistently configured across all devices. The VLAN IDs and tagging should match on both the FortiSwitch and the HPE switch.

  5. Monitor Traffic and Resource Usage: Before making changes, monitor the FortiGate's resource usage. Use the `get system performance status` command to check CPU and memory usage.

  6. Test in a Controlled Environment: If possible, test the configuration in a lab environment or during off-peak hours to minimize impact.

  7. Backup Configuration: Always backup the current configuration before making changes. This allows you to quickly revert if something goes wrong.

  8. Consult Documentation and Support: Review Fortinet's documentation for best practices on VLAN and trunk configurations. If needed, consult Fortinet support for guidance specific to your setup.

 

By following these steps, you can minimize the risk of network disruption during your migration.

Jean-Philippe - Fortinet Community Team
507adminJ
507adminJAuthor
New Member
September 18, 2025

Thanks,

 

How would I go about consulting Fortinet support for guidance specific to our setup? Ultimately, I think that is what I would like to do, but it seems like I cannot obtain support unless I have something specifically not working.

Terms & ConditionsAccessibility statement