As others have mentioned there are multiple options. If you want micro-segmentation (one network per app-tier) with fine-grain access control you can use the OpenContrail plugin https://github.com/Juniper/contrail-kubernetes. It has the added advantage that you have a tenant network span k8s, openstack, vlans, or anything else you can plug into a reasonable mid-tier router.

[Disclosure: i'm currently working on this project]