No idea how to do port monitoring/mirroring in specific case [on hold]

I have a problem with port monitoring idea. Description : In one ESXi area, we have few VMs – bricks of one voice system. One of those VMs is a SBC – connector between the company enviroment and Service Provider. I wanted to do a sniffer on PC which will be connected to one of the ports on the same switch where is this ESXi’s interface connected using the port monitoring (source/destination), but i cannot do it on Cisco nexus, because it is an aggregating switch. I also know that in this topology i will recieve all the traffic from the ESXi’s inside, but this sniffer will take only SIP/RTP protocols signalization. So maybe you will know what can i do in this situation and where can i phisically pług this PC in order to sniff those packets. Tcpdumps on this SBC VM is not a good optima because it is affecting on the SBC performance so thats why i thought about port monitoring which in my opinion and that specific case is noninvasive. So maybe do you know how to perform it as easy as possible with talking care about performance?? And where should i pług in this sniffer phisically?