Ipsec from one host inside LAN trouble with 2 DSL line

[sap68]

Hi,

Since I install a second DSL line and use the 2 line for balance traffic with a pfsense 2 (just gateway balance), I have problem to maintain UP an IPsec with an external firewall and my laptop.

I launch the client on my laptop, VPN goes UP and run for some minutes then it stop and never work anymore until I reconnect my VPN client.

Maybe it's a problem with round robin access to internet?
What kind of rules must I insert in pfsense to force outside  connection Ipsec to only a DSL line?

Or maybe it's another problem that I'm not aware?

Thanks in advance.