It depends on how your network is setup; but usually the IP is not stripped and the packet headers contain the original source and destination.
Generally, a core switch comes after a router, the router is likely on an enterprise network to be doing a lot of NAT translations. In which case, you may see the NAT IP of a given packet be referenced (e.g instead of some public ip, you see 192.168.x.x). So it's likely you will see the internal IP as a source of anything outbound, because, that's the only IP the network device knows about -- the external IP is applied by the router doing NAT.
However unless you're doing some strange (e.g. Cisco fix-up) packet-level inspection and changing, the packet headers should remain the same and indicate the source and destination IP of the endpoints -- not of any intermediate network devices that carry the traffic. Those devices only have management IPs -- and don't tend to (although this can happen in sophisticated layer 3 switching setups which are uncommon) alter the packet headers.