I you are looking to enable telnet access to the Netgear R7800, have a look at below instructions, and a word of warning, some consider telnet access a weakness, so do not forget to disable Telnet Access afterwards
From you browser, enter the following URL,
http://192.168.1.1/debug.htm (substitute 192.168.1.1 if your routers IP address is different)
Enter Routers ‘Admin’ Username and Password.
You will be presented with the below screen in your Browser, select the Enable Telnet check box.
Enjoy and do not forget to turn of telnet afterwards.
Note: unsure if this works with other Netgear Routers, so worth a try?
This hidden page also give you access to :
CPU Load
Memory Usage(Used/Total)
Flash Usage(Used/Total)
Network Session(Active/Total)
System Uptime
Debug Log Capture
Enable Telnet
WAN Port mirror to LAN port1
Allow external IPv6 hosts ping internal IPv6 hosts
Enable 11k