The user does not need to allocate loopback ports on the 7210 SAS-D. They are allocated by the software and can be displayed using the show system internal-loopback-ports command.
The following output is an example of internal-loopback-ports information. The output shows that virtual port 1/1/11 and 1/1/13 are allocated for MAC-swap and testhead application.
A:Dut-B# show system internal-loopback-ports
===========================================================================
Internal Loopback Port Status
===========================================================================
Port Loopback Application Service Speed Type
Id Type Enabled 1G/10G
---------------------------------------------------------------------------
1/1/11 Virtual Mac-Swap No 1G
1/1/12 Virtual Dot1q-Mirror No 1G
1/1/13 Virtual Testhead No 1G
===========================================================================