Zyxel VMG8924-B10A as a wifi repeater

I am using the above router purely as a wifi repeater connected to a switch and an Asus router to connect to my modem.

Every now and again my Netmeter on my machine spikes an upload every say 2 minutes but if I unplug the repeater the upload spike stops.

Any ideas what data my machine is sending or how to find out and why it stops when I unplug the zyxel?

I have found out what the spike is, it is SSDP keep alive sending from my main PC to my other PCs over wifi. Glad I found out what it was it was doing my OCD in.