The WS-C2960X-48FPD-L has 48 interfaces that are 10/100/1000, and 2 uplink interfaces that are SFP+.
Each 10/100/1000 interface has a maximum link speed of 1,000 Mbps = 1 Gbps = 1,000,000,000 bits per second.
Each SFP+ interface has a maximum link speed of 10 Gbps = 10,000,000,000 bits per second.
For each packet transmitted on an Ethernet link, there are 12 bytes of Inter Frame Gap, followed by 7 bytes of MAC Preamble and then a 1-byte of Start of Frame Delimiter, adding up to 20 bytes of overhead (12+7+1=20). Next, add to this a minimum-size Ethernet frame of 64 bytes, which consists of a 6-byte Destination MAC Address, then a 6-Byte Source MAC Address, then a 2-byte MAC Type or length, a minimum Network Payload of 46 bytes, followed by a 4-byte CRC (6+6+2+46+4=64), and you get a total of 84 bytes (20+64=84) involved in the transmission of that packet. Since there are 8 bits per byte, that 84 bytes can also be thought of as 672 bits (84*8=672).
If you divide 1,000,000,000 bits per second by 672 bits per 64-byte packet transmitted, you get 1,488,095.238095 which is the maximum number of 64-byte packets you can transmit per second on a 1-Gbps connection.
Multiply that by 10 to get 14,880,952.380952 which is the maximum number of 64-byte minimum-sized packets you can transmit on a 10-Gbps connection.
48 interfaces of 1-Gbps transmitting 64-byte packets gets you 71,428,571.428571 packets per second, or pps. (48*1,488,095.238095).
2 interfaces of 10-Gbps transmitting 64-byte packets gets you 29,761,904.761904 pps. (2*14,880,952.380952).
Add those two multi-million numbers together, and you get 101,190,476.190475 pps. (71,428,571.428571+29,761,904.761904).
That number looks like it is still short of the 130.9 Mpps quoted on the Data Sheet. About 2 10-Gbps interfaces short, in fact. Is there a way we can get 2 more 10-Gbps interfaces into a 2960-X that already has 48 10/100/1000 and 2 SFP+ interfaces? Yes!
If you install a C2960X-FIBER-STK FlexStack-Extended Fiber stacking module, that will give you two more SFP+ interfaces on the back of the switch. They are in stack mode by default. But you can convert them to network mode, which give you another 2 interfaces of 10-Gbps.
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960x/software/15_2_6_e/configuration_guide/b_1526e_consolidated_2960x_cg/b_1526e_consolidated_2960x_cg_chapter_01010010.html#id_33181
So, 101,190,476.190475 pps from the 2960-X switch itself + 29,761,904.761904 more pps from the FlexStack-Extended Fiber stacking module installed in it with those 2 SFP+ stack ports converted to network ports, equals 130,952,380.952379 pps total. That's probably where they got 130.9 Mpps for the forwarding rate on the Data Sheet.
Hope this helps.
