Capture packets before the VPN encryption

Hi,

I'm using a softphone which registers to a IP PBX using a L2TP/IPSEC VPN. When I try to capture the packets sent, I only see the EPS Packets... But The packets are being sent from my PC, so I should be able to capture them BEFORE the encryption takes place, right? How can I do it?

Is there any alternative solution?

Regards. Daniel