there are several possible causes and troubleshooting steps you can try:

1. Basic troubleshooting:

    Verify cable connections: Ensure all network cables are securely plugged into the correct ports on the Sangfor firewall and other network devices. Faulty or loose cables can significantly impact data transfer speeds.
    Reboot devices: Sometimes, a simple reboot of the Sangfor firewall and other network devices can resolve temporary glitches or software issues.
    Check for errors: Look for any error messages in the Sangfor firewall logs or event viewer on other devices. These may provide clues about the source of the slow speeds.

2. Sangfor firewall configuration:

    Inter-VLAN routing: Make sure inter-VLAN routing is enabled on the Sangfor firewall for the specific VLANs experiencing slow speeds. You may need to consult the Sangfor documentation for specific configuration steps.
    QoS settings: Check if any Quality of Service (QoS) settings are applied on the Sangfor firewall that might be prioritizing other traffic over data transfers between VLANs. Adjust QoS settings if necessary to prioritize data transfers.
    Security policies: Review any security policies applied to the VLANs that might be throttling data transfer speeds. For example, if you have intrusion detection or prevention systems enabled, they might be impacting performance.

3. Network equipment:

    Check for overloaded interfaces: If the interfaces on the Sangfor firewall or other network devices are overloaded with traffic, it can lead to slowdowns. Use monitoring tools to check interface utilization and identify any bottlenecks.
    Faulty hardware: Although less likely, it's possible that faulty hardware on the Sangfor firewall or other network devices could be causing the slow speeds. If you've exhausted other troubleshooting options, consider replacing any suspected hardware.

4. Additional tips:

    Upgrade firmware: Ensure you're using the latest firmware version for the Sangfor firewall and other network devices. Outdated firmware can sometimes cause performance issues.
    Contact Sangfor support: If you've tried all of the above troubleshooting steps and are still experiencing slow speeds, contact Sangfor support for further assistance. They may be able to provide more specific guidance based on your network configuration and logs.

there are several possible causes and troubleshooting steps you can try:

1. Basic troubleshooting:

    Verify cable connections: Ensure all network cables are securely plugged into the correct ports on the Sangfor firewall and other network devices. Faulty or loose cables can significantly impact data transfer speeds.
    Reboot devices: Sometimes, a simple reboot of the Sangfor firewall and other network devices can resolve temporary glitches or software issues.
    Check for errors: Look for any error messages in the Sangfor firewall logs or event viewer on other devices. These may provide clues about the source of the slow speeds.

2. Sangfor firewall configuration:

    Inter-VLAN routing: Make sure inter-VLAN routing is enabled on the Sangfor firewall for the specific VLANs experiencing slow speeds. You may need to consult the Sangfor documentation for specific configuration steps.
    QoS settings: Check if any Quality of Service (QoS) settings are applied on the Sangfor firewall that might be prioritizing other traffic over data transfers between VLANs. Adjust QoS settings if necessary to prioritize data transfers.
    Security policies: Review any security policies applied to the VLANs that might be throttling data transfer speeds. For example, if you have intrusion detection or prevention systems enabled, they might be impacting performance.

3. Network equipment:

    Check for overloaded interfaces: If the interfaces on the Sangfor firewall or other network devices are overloaded with traffic, it can lead to slowdowns. Use monitoring tools to check interface utilization and identify any bottlenecks.
    Faulty hardware: Although less likely, it's possible that faulty hardware on the Sangfor firewall or other network devices could be causing the slow speeds. If you've exhausted other troubleshooting options, consider replacing any suspected hardware.

4. Additional tips:

    Upgrade firmware: Ensure you're using the latest firmware version for the Sangfor firewall and other network devices. Outdated firmware can sometimes cause performance issues.
    Contact Sangfor support: If you've tried all of the above troubleshooting steps and are still experiencing slow speeds, contact Sangfor support for further assistance. They may be able to provide more specific guidance based on your network configuration and logs.