Cisco SPA2102 - Miscellaneous Settings Section; System Reserved Ports Range Section

ATA Routing Field Reference
Application page
Cisco Small Business ATA Administration Guide 109
A
Miscellaneous Settings section
System Reserved Ports Range section
Multicast Passthru Used for passing multicast traffic. Options are disabled,
inbound, outbound, inbound and outbound.
Starting Port A port identified as a reserve port and that is not used
for NAT translation. That is, if there is a conflict  if port
forwarding is set on the same port  then the port
forwarding is cancelled. Default is 50000.
Num of Ports Reserved Total number of ports reserved. Options are: 256, 512,
and 1024.