For D-link DSL 2750u, found an external way to reconnect through telnet scripting tool v1.0 by Albert Yale. Link: freewareweb.com/cgi-bin/archive.cgi?ID=645

Here's the script:
192.168.1.1 23
WAIT "username:"
SEND "admin\m"
WAIT "password:"
SEND "xxxx\m"
WAIT
SEND "reboot\m"
WAIT
SEND "exit\m"
SEND "y\m"

Save the above in a txt file and configure JD reconnect to select 'External Tool Reconnect'. Set the path of the tool 'C:\TST\TST10.exe' properly and in the parameter tab enter: /r:Reboot_Dlink_DSL2750u.txt

Alternatively can create a bat file with one line as below:
C:\TST\TST10.exe /r:Reboot_Dlink_DSL2750u.txt

In JD Advanced settings change Reconnect: Seconds To Wait For IPChange = 150 & Reconnect: Seconds To Wait For Offline = 120.