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Overlapping VLAN Support Using Multiple Forwarding Instances or VLAN Normalization

In platform-as-a-service (PaaS) and infrastructure-as-a-service (IaaS) deployments, each customer uses a separate physical interface to connect to a leaf device. In this situation, you can't use the same VLAN ID for two different tenants in separate MAC-VRF instances that share the same default forwarding instance. However, you can have a VLAN name with the same VLAN-ID (for example, vlan200 with VLAN ID 200) in two different MAC-VRF instances if they each have their own forwarding instances. You can also configure explicit or implicit VLAN normalization using service provider style interface configuration.

You can configure forwarding instance identifiers on the QFX10000 line of switches and ACX7100-32C and ACX7100-48L devices.

We support overlapping VLANs on some platforms that don’t support multiple forwarding instances. See Overlapping VLAN Support Using VLAN Translation in EVPN-VXLAN Networks for more information.

Note:

On the QFX10000 line of switches, you can configure up to 99 forwarding instance identifiers.

On ACX7100-32C and ACX7100-48L devices, you can configure up to 6 forwarding instances.

Benefits

  • Enables overlapping VLANs

  • Identifies which customers are sharing VLANs

Overlapping VLANs Using the Enterprise Style Interface Configuration

Overlapping VLANs with Multiple Forwarding Instances

This configuration allows overlapping VLAN-ID 200 in different MAC-VRF instances by configuring separate forwarding instances.

Overlapping VLANs Using the Service Provider Interface Style Configuration

Implicit Normalization With VLAN ID Sample Configuration

This configuration implicitly translates the customer VLAN ID to the VLAN ID specified in the bridge domain upon ingress. At egress, the VLAN ID used to normalize the bridge domain is removed, and the customer VLAN ID is pushed onto the frame. In this case, the overlapping VLAN IDs of 150 are mapped to VLAN ID 200 and 400, respectively. In this example, the subscriber traffic is transported over the EVPN core using VXLAN VNI assignments that match the normalized VLAN IDs.

Implicit Normalization with VLAN ID None Sample Configuration

This configuration implicitly normalizes the two overlapping customer VLANs to unique VLAN IDs within their respective bridge domains. At ingress, the customer VLAN ID is stripped and the (now) untagged traffic is transported over the EVPN VXLAN fabric. At egress on the customer interface, the VLAN tag is pushed back onto the frame. In the EVPN core, the two customer VLANs, which both use VLAN ID 150, map to VXLAN VNIs 200 and 400, respectively.

Explicit Normalization with VLAN Maps

Explicit normalization does not specify a VLAN ID in the bridge domain. Instead, VLAN map operations are used to manipulate the VLAN label stack to achieve the desired normalization. In this example, two customers use the same VLAN ID of 150. The input and output maps applied to the interface explicitly swap the customer tag with the normalized assignments used in the provider network. In the egress direction, the swap operation causes the interface's VLAN tag to be swapped onto the frame.

Explicit normalization is needed when using the vlan-bundle service type for the instance.

Note: VLAN map operations are supported only on service provider style interface configurations. IRB interfaces are not supported within the bridge domain with this method.

Multiple Forwarding Instances Sample Configuration

This configuration is similar to the enterprise style interface configuration. You use separate forwarding instances to allow overlapping VLAN-ID 200 in different MAC-VRF instances.

Related Documentation