Overview of VLAN Services for EVPN
A Data Center Service Provider (DCSP) hosts the data center for its multiple customers on a common physical network. To each customer (also called a tenant), the service looks like a full-fledged data center that can expand to 4094 VLANs and all private subnets. For disaster recovery, high availability, and optimization of resource utilization, it is common for the DCSP to span across the data center to more than one site. When deploying the data center services, a DCSP faces the following main challenges:
Extending Layer 2 domains across more than one data center site. This requires optimal intra-subnet traffic forwarding.
Supporting optimal inter-subnet traffic forwarding and optimal routing in the event of virtual machine (VM).
Supporting multiple tenants with independent VLAN and subnet space.
The DCSP might require Ethernet VLAN services to be extended over a WAN with a single EVPN instance (EVI). Junos OS supports VLAN-based service, VLAN bundle service, and VLAN-aware bundle service, while maintaining data and control plane separation. The following figures illustrate the relationship between VLANs and EVIs.
Figure 1 illustrates a VLAN-based service where you have a one-to-one mapping between a VLAN ID and a EVI.
Figure 2 illustrates a VLAN bundles service where you can have one EVI mapped to many VLAN IDs in a single bridge domain. The bridge table is shared among the VLANs.
Figure 3 illustrates the relationship between VLANs and EVIS in a VLAN-aware bundle service where you can have one EVI mapped to many VLAN IDs. Each VLAN has a different bridge table.