A network appliance is used as an EC2 router between subnets. Routes target its network interface, but transit traffic is dropped despite correct appliance rules. Which instance setting is relevant?

1. Attach an S3 gateway endpoint to the appliance process.
2. Enable source/destination checking to force the instance to accept transit packets.
3. Change the instance Name tag to router.
4. Disable source/destination checking on the forwarding instance.