L2TP/Ipsec DNS PROBLEM

Hi,

I have a little problem with my DNS request when behind my VPN

To make it “simple”

I have a mikrotik acting as a core router / dialing up pppoe, and windows 2008r2 ad

My mkt for DNS request has : the ip of my ad (for all the necessarry request), and the peer dns provided by my ISP, and ALLOW REMOTE REQUEST checked

When i connect my vpn (the bridge it connect on is on proxy-arp) everything works fine except one thing the DNS

If in the vpn profile i set DNS : Ip of the MKT, i can’t ping any of the DNS entry of my AD
If i set inside the IP of my AD directly, it works like a charm

Can someone explain me what i m doing wrong ?

Thanks a lot

Andy