deis/router#167
This issue from Deis upstream was really informative, but it was also written mostly before Deis v2 reached GA.
The conclusion of the issue was evidently that, an alpha feature in K8S v1.4 would enable the correct behavior in the L7 load balancers provided by GKE, through the service.alpha.kubernetes.io/external-traffic: OnlyLocal annotation.
There have been several versions released since v1.4, and according to the docs I guess this annotation is now in beta in newer versions:
https://kubernetes.io/docs/tasks/access-application-cluster/create-external-load-balancer/
Does anyone have more information about the state of the external-traffic ingress annotation and how it interacts with Router?