Can't connect to L2TP LNS with the same gateway IP

Hello everyone.

I’m using PPPOE connection, and on top of that i’m trying to connect to L2TP server.
This ISP i’m connecting to over L2TP has 2 LNS: lets say first one is 5.5.5.5 and 2nd one is 6.6.6.6.

When you connect to the 5.5.5.5 LNS, you get gateway of 5.5.6.6 , in this case i’m able to connect and get RX and TX outside.
When you connect to the 6.6.6.6 LNS, you get gateway of the same IP of the LNS 6.6.6.6, in this case i’m able to connect but unable to receive data.

When trying to connect to the LNS, i added static route of : DST IP-5.5.5.5 , Gateway-PPPOE client. I did that for both of the LNS.
But it seems that as long as the LNS is the same IP address of the gateway i’m getting after connecting to the L2TP, i wont be able to surf and the L2TP will go down after 1 minute on its own.

Looking at the route tables i can see that wenh i’m connecting to the 6.6.6.6 LNS, right after i connect to it, the static route that i added of DST ADDR-6.6.6.6 , gateway-PPPOE, is being canceled (becomes blue). While connecting to the LNS that gives different Gateway IP than the LNS the static route stays working.

By the way, if i try to connect to L2TP via Windows, i’m able to connect/surf with both of the LNS.

How can I overcome this problem? what am i doing wrong? or what should i do?
(if i miss some info please let me know).