Regarding the network issue, it's possible that the network configuration is not compatible with your QEMU environment. You may need to check the network settings in the Sangfor NGAF image and adjust them accordingly to work with your QEMU environment.

You can also try accessing the NGAF web interface using the IP address assigned to another interface, if available. If none of the interfaces work, you may need to check the network configuration in your QEMU environment and ensure that it's properly configured to allow communication between the host and the VM.

If you continue to have issues with accessing the Sangfor NGAF image in QEMU, you may want to consider using a different hypervisor that's compatible with the image, or contacting Sangfor support for further assistance.

Follow this link,

https://foswiki.org/Support/HowToRunVirtualMachineImageOnKvmQemu

Please check if properly converted to ova file

I think QEMU does not support

QEMU transfers the remaining memory data to the destination host at one time, then the destination host starts running, and the source host shuts down.

Thanks for sharing

In the initial stage of migration, the source host starts an identical virtual machine on the destination host through the negotiation mechanism and puts it into a quiesced state.
After the source host QEMU records all the memory data of the virtual machine, it is transmitted to the destination host through the network. However, since the running business will read and write memory data during the transmission process, the newly generated memory data will be re-recorded after the first round of transmission is completed. It will transmit it to the destination host in the same way, and iterate in turn until the last recorded memory data meets a threshold, the source host will stop running- that is, only 1 second of service interruption duration.
QEMU transfers the remaining memory data to the destination host at one time, then the destination host starts running, and the source host shuts down.