On Networks N150RM User Manual - Manual (Page 61)

Advanced Settings
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N150 Wireless ADSL2+ Modem Router N150RM
advertisement time to live is 4 hops, which is fine for most home networks. If you notice
that some devices are not being updated or reached correctly, it might be necessary to
increase this value.
UPnP Portmap Table . The UPnP Portmap Table displays the IP address of each UPnP
device that is accessing the modem router and which ports (internal and external) that
device has opened. The UPnP Portmap Table also displays what type of port is open and
whether that port is still active for each IP address.
3. Click Apply to save your settings.