Overlapping VLAN Support Using VLAN Translation in EVPN-VXLAN Networks

Benefits

• Simplifies re-provisioning a network after combining different business areas in the network that might use the same VLAN IDs for different functions.

• Helps service providers to maintain traffic isolation in the same network among different customers using one or more of the same VLAN IDs.

Overview

When you configure VLAN translation, you map the host VLAN ID in tagged packets coming in on an interface to a configured VLAN ID. We call that configured VLAN ID a mapped VLAN value. For ingress packets from the host, the device substitutes the mapped VLAN value for the host VLAN ID before the packet enters the packet processing pipeline. On egress when forwarding tagged traffic toward the host, the device replaces the mapped VLAN value with the host VLAN ID.

You use the usual VLAN configuration statements to define the VLANs you plan to use as mapped VLAN values. You also associate interfaces with those VLANs. Then to configure the VLAN translation, use the vlan-rewrite translate from-vlan-id to-vlan-id statement at the [edit interfaces interface-name unit logical-unit-number family ethernet-switching] for each host VLAN mapping and interface as needed. With this statement:

• The from-vlan-id is the host VLAN ID.

• The to-vlan-id is the mapped VLAN value.

You can specify host VLAN IDs and mapped VLAN values in the usual VLAN range—1 through 4094.

If you configure an interface with multiple host VLANs and map some (but not all) of those host VLANs to mapped VLAN values, the interface:

• Accepts and passes through packets that are tagged with host VLAN IDs that are not mapped (host VLAN IDs that have no corresponding vlan-rewrite translate statement).

• Accepts packets that are tagged with a host VLAN ID for which the interface has a vlan-rewrite translate configuration. The interface drops packets that are tagged with the corresponding mapped VLAN value.

For example, the following configuration includes VLANs 100 and 101 on interface xe-0/0/1. The configuration also establishes VLAN translation for host VLAN ID 200 to mapped VLAN value 100.

With this configuration, the interface:

• Accepts incoming packets that are tagged with VLAN 101 because that VLAN isn't mapped.

• Accepts incoming packets that are tagged with VLAN 200 because that VLAN is a host VLAN with a vlan-rewrite mapping.

• Drops incoming packets tagged with VLAN 100 because that VLAN is a mapped VLAN value for host VLAN 200.

Supported VLAN Translation Configurations

We support VLAN translation on an interface as follows:

• You can map a host VLAN ID to a mapped VLAN value only on access interfaces with enterprise style interface configurations.

• You can map each host VLAN to one and only one mapped VLAN value.

  You'll see a commit error if you try to configure VLAN translation of the same host VLAN to more than one mapped VLAN value.

  For example, the following configuration includes VLAN IDs 100 and 101 on interface xe-0/0/1. The configuration also maps host VLAN ID 200 to mapped VLAN value 100.

  If you then try to map the same host VLAN 200 to the other configured VLAN 101 on the same interface, the CLI won't allow the commit:

• You can map only one host VLAN to the same mapped VLAN value on an interface.

  In other words, after you map a host VLAN, you can’t map a different host VLAN tag to the same mapped VLAN value on the same interface. The CLI doesn't block the commit operation, but only the most recent mapping will take effect.

  For example, you configure VLAN 100 on an interface, and map host VLAN 200 to mapped VLAN value 100:

  You commit that configuration, then configure a mapping from host VLAN 300 to the same mapped VLAN value 100:

  The device overwrites the first mapping with the second one for that mapped VLAN value, and processes packets only according to the second mapping.

• You can map different host VLANs to different mapped VLAN values on the same interface.

  For example, if you configure VLANs 100 and 101 on an interface, you can map host VLAN 200 to one mapped VLAN value (100) and host VLAN 300 to another mapped VLAN value (101) on that same interface:

• You can map the same host VLAN to the same mapped VLAN value on different interfaces.

  For example, if you configure two interfaces xe-0/0/1 and xe-0/0/2 as members of VLAN 100, you can map host VLAN 200 to the same mapped VLAN value (100) for both interfaces:

• You can map different host VLAN tags to the same mapped VLAN value on different interfaces.

  For example, your configuration includes VLAN 100 on interfaces xe-0/0/1 and xe-0/0/2. You can map host VLAN 200 on xe-0/0/1 and host VLAN 300 on xe-0/0/2 to the same mapped VLAN value 100:

Verify VLAN Translation Mappings on an Interface

Run the show ethernet-switching interface interface-name detail CLI command to verify the VLAN translation mappings on an interface.

For example, consider again the case where you configure different VLANs (VLAN 100 and VLAN 101) on the same interface, xe-0/0/1. Then you map different host VLAN IDs (200 and 300) to each of those mapped VLAN values (100 and 101, respectively).

In the output from the show ethernet-switching interface xe-0/0/1 detail, you see the host VLAN ID (200 or 300) in the Trunk id: output field. You also see the corresponding mapped VLAN value (100 or 101) in the VLAN id: output field, and its configured VLAN name (vlan100 or vlan101) in the VLAN name: output field.