Well, i think u took it in different way, NNI and UNI are Network Port Types, for Isolating purpose, and Access and Trunks are operational attributes.
UNI Cannot Talk with UNI Port --Either its Access or Trunk.
NNI can Talk with NNI and UNI port --> its similar like Private VLANS.
NNI port will always be your Trunk or uplink port, it can also be your access port as well.
In UNI port you will connect your customers, and most probably it will be Access port.
In NNI port you will connect your uplink, and most probably it will be your Trunk port or could be your access port.
As per official Doc:
Q. What is UNI/NNI?
A. UNI/NNI is the classification of port types designed for the Metro Ethernet market. UNI, User Network Interface, is the interface that faces the subscriber, and NNI, Network Node Interface, is the interface that faces the service provider network. By labeling each port as UNI or NNI, the software can optimize each port for its role.
Re: uni port vs access port ---- nni port vs trunk
The choice of access vs. trunk port (on UNI's) is also dependent on the customers requirements and the type of ME service (EPL or EVPL) the customer will need.
This can also be tricky. Generally, if the customers CE's are routers, you can provide either an Access Port if the routers interface is a "routed port". Or if the customers CE has a trunk port (sub-interfaced), then you would need to provision a Trunk Port. Because both of these scenarios are "customer-facing" ports, and as above-mentioned by our colleague, they will almost always be UNI ports, not NNI ports. Customer-facing NNI's are generally used in managed-CE scenarios.
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