I am using Cisco's HA network design. My one question in the design is; in the distribution why have they configured a loopback and lableled it "Garbage-CAN RP" and then labeled another RP as Good-IPMC? I have never used a loopback in my multicast configuration before. Check out page 94 in the pdf I have attached on the distribution side. Notice they have configured a bad RP and a good RP what is the premise behind this?