Airport extreme lan speed drops

Hi guy's,

I have an Dlink 6740 that works as a bridge, all my network (WiFi and LAN) is going through my Airport Extreme.

In wifi my speed is 50 MBPS +- but Recently I noticed that I had a speed problem when I connected with lan to the AIrport, so I did a speed test and I was surprised to find out that when i'm connected with lan my speed is 5 MBPS..

So in wifi i have 50 and in lan i have 5..

In the Airport setting in internet i'm in PPPOE and that's all...

I'm getting this speed in any Lan port on the Airport. Tried to unplug it from electricity. nothing. the same speed..

I do not even know where to start looking at this problem, because i didn't change any settings lately..

Regards,

Moti