I'll get back to BGP at some point here, but I thought I would mention this interesting find. While I was skulking about looking for some good CISSP materials, I found this podcast, and found the one episode I heard very interesting as it was discussed from the point of view of experienced TAC engineers. The episode I grabbed was about GETVPN and DMVPN and was quiet good. Definitely worth checking out if you like the intersection of security and Cisco.