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How to send multiple VLANs across a link using only one tag

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TitleHow to send multiple VLANs across a link using only one tag
Objective
Often it may be necessary to send multiple VLANs across a service provider layer 2 service to bridge one or more physical locations.  However, in some situations the service provider may only allow a single tagged VLAN to transit the service provider network.  In this particular scenario a VMAN can be used, as a workaround, to encapsulate multiple VLANs into a single VMAN.

This same workaround can also be applied in a scenario where customer VLAN traffic must be encapsulated into a VMAN at the customer edge switch (i.e. the customer VLANs are present on the same switch as the ingress point to the VMAN)
Environment
All EXOS
Procedure
 In a typical VMAN scenario at least four devices are required, two customer edge devices and then the two provider edge devices to which they connect:

Typical VMAN Example

In this scenario, the customer edge and provider edge must be collapsed into a single device.  This workaround involves using a physical "loopback" port on the customer edge switch to encapsulate the customer VLANs into the VMAN.  


Note: Jumbo frames must be supported across the service provider connection.

VMAN Topology with Loopback

Customer Edge 1 and 2 Configuration

1. Create the vlans and add them tagged to the "Customer Edge" side of the loopback (port 1):
create vlan purple tag 10
cerate vlan orange tag 20
create vlan green tag 20
configure vlan purple add port 1 tag
configure vlan orange add port 1 tag
configure vlan green add port 1 tag
2. Create the VMAN and add the "Provider Edge" side of the loopback (port 2) to it untagged.  Add the uplink to the service provider (port 3) to the VMAN tagged:
create vman sp tag 100
configure vman sp add port 2 untagged
configure vman sp add port 3 tagged
enable jumbo-frame port 2,3
3.  Typically the Service Provider will be expecting the traffic to have an ethertype of 0x8100.  If that is the case, the VMAN ethertype will need to be changed to 0x8100:
configure vman ethertype 0x8100


 
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