I have a Cisco Catalyst 3750X switch, and I have configured port mirroring on it. Traffic from 12 of the 1G ports will be mirrored to both 10G ports, and I have connected both 10G ports to a server that captures the traffic.
Currently, I have one of the 12 1G ports connected to another server that replays a pcap file once at maximum speed (i.e. option -t in tcpreplay). I thought that this setup means I should get twice the number of packets (and rate) from the two 10G ports. However, I noticed that although the original pcap file contains 4288 packets, the number of packets from the two 10G ports varies between 31000 to 34000 packets, which is about 7 to 8 times the original number of packets.
Why am I getting more than twice the amount of traffic, and why does the output vary?