How to protect lan port

[wachu13]

Hello
I have Asus RT-N66 as a main router. To reach part of the house I run a wire to second location and install second router (Linksys) which working in bridge mode. Is there any way to create something like guest network on Asus router but for that lan port?
I needs to protect against situations like someone will connect different router in place of Linksys or connect directly skipping router.
Thanks for any ideas.

 

[sfx2000]

superglue the plug into place?

 

[CaptainSTX]

If you trim off the end of the locking tab on the male plug after it is plugged into a female jack it make it difficult to remove without a tool. Otherwise as sfx2000 said superglue will prevent removing a male plug.