@David-TP thanks for replay .. i power on the 2 deco via dc power adapter which came with the deco and i tried to replace the ethernet cable ... i thought its because of it ( by the way its cat 5e )...

i have some issues with this deco x50 outdoor 1- sometimes it shows Abnormal WAN Port speed .... and the downlosd and upload speed go low when this show up.... so the only way i fix this problem is...