Over time, the ZyXEL access points, specifically the WRE6505 tends to degrade performance and it must be reboot to fix the problem. Usually you can just login to the web interface and reboot devices like this remotely, but unless I'm missing it there is no way to reboot those things through the web GUI. But there is still a way to do it remotely: telnet!
If you're on windows, you have to go to "Programs and Features -> Turn Windows Features On and Off" and enable the telnet client before you can use telnet. If that isn't enough direction, I'm sure you can Google it to find better instructions.
The ZyXEL WRE6505 runs on the Linux platform and has a telnet server running by default. Interestingly, there are two different ways to login to the WRE6505: admin and root.
The admin user gives limited control over the telnet environment and rebooting using this login is not permitted. So, you have to instead login as root.
I was curious if the password for the GUI, automatically updated the password for telnet, so I tested it out. The GUI password does update the admin and root passwords, but ONLY if you've reboot the entire system after a password change. Meaning, if you change the password in the GUI, the password for telnet will remain the old password until a full reboot has happened. Personally, I find this to be a slight security risk but whatever. The ZyXEL WRE6505 is a cheap home access point that has a very low likelihood of being hacked. The only time it should be of concern is if you use it in a public place like a coffee shop and like I said, a full reboot will fix the security hole if you're updating the password from the default 1234.
How To Reboot A ZyXEL WRE6505 From Command Line
Moving on, the procedure to login and reboot is as follows:
Telnet into the access point (IP may be different. default is 192.168.1.2)
Login as root with your password
zyxelsetup login: root
Issue the "reboot" command
Done! Wait for the AP to reboot and you're good to go.