ARP protocol in GCP for two VMs to communicate directly

Question

I have two machines within GCP. Both machines are on the same subnet.

The way I understood, GCP is build on SDN and so there is not traditional switching. In other words, there is no ARP recognition for my two machines to communicate directly to each other omiting default gateway.

Am I right? can you please shed some light onto it?

Answer 1

ARP and RARP are supported. ARP lookups are handled in kernel software. Once the two systems have communicated, the OS know each other and there is IP and MAC mapping. If the systems have not communicated then the MAC mapping takes place in the VPC. These VPC's use Linux's VITRIO network module to model Ethernet card and router functionality.