Virtualization adds a network layer inside each server. Virtual switches connect VMs to each other and physical networks.
Virtual switch functions:
- Connect VMs on same host
- Forward to physical NICs
- Apply VLANs and policies
Common virtual switches: VMware vSwitch, Open vSwitch, Linux Bridge, Hyper-V Virtual Switch.
Uplinks: Use multiple NICs for redundancy. Use LACP for aggregation.
Traffic between VMs on the same host stays inside. Physical network never sees it. Efficient but invisible to monitoring.