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An ENNI port is also known as an “external network-to-network interface,” as defined in MEF 26.
ENNIs allows Q-in-Q tunneling, also known as IEEE 802.1ad or “stacked VLANs.” While carriers commonly use this to manage customer traffic, individuals might have various uses for Q-in-Q as well.
For more information on business use cases, see Announcing ENNI Support for Q-in-Q, Network Extension and Backbone Expansion.
With Q-in-Q tunneling, an Ethernet frame has two VLAN tags:
- C-VLAN - Also known as the “Customer VLAN.” This is the inner tag.
- S-VLAN - Also known as the “Service VLAN.” This is the outer tag.
You can use the S-VLAN to bundle and direct traffic, while still maintaining the C-VLAN identifier.
- The default TPID value is 0x8100.
- You cannot combine non-ENNI and ENNI ports together in a LAG.
Use cases - ENNI to non-ENNI
Untagged frames enter the access port
As the frame enters the ENNI, it has stacked VLAN tags. At the ENNI, both tags are dropped. When the frame leaves the access port, it is untagged.
Untagged or tagged frames enter the access port
As the frame enters the ENNI, it is only tagged with the outer S-VLAN tag. The S-VLAN tag is dropped at the ENNI. When the frame leaves the access port, it is untagged. However, if there was a C-VLAN tag, it would remain.
This is similar functionality to our EPL solution, point-to-point connections.
Tagged frames enter the access port
As the frame enters the ENNI, it has stacked VLAN tags. The S-VLAN tag is dropped at the ENNI. When the frame leaves the access port, it has the C-VLAN tag, which serves as the VLAN ID.
This is the most common use case.
Combined use cases
You can use a single ENNI to combine all these use cases for a custom networking solution:
Use case - ENNI to ENNI
This is a common service-provider use case. All traffic is passed using the S-VLAN.