Let the NIC router provide an Uplink service besides the Nic service that it
already provided. Requests for an Uplink session towards the NIC router are
assigned to Domains using the same <policy> configuration tags that are used in
order to assign Nic session requests. The MAC addresses of Uplink session
components are _NOT_ considered during the allocation of MAC addresses for NIC
session components at the same Domain. The task of avoiding MAC address clashes
between Uplink session components and Nic session components is therefore left
to the integrator. Apart from that, Uplink session components are treated by
the NIC router like any other interface.
Ref #3961
