The subcards in the front slot and rear slot use the same chip that provides 4x10 Gbit/s bandwidth. Therefore, the S5300EI or S5300SI stacks set up through stack cards have the following limitations:

A stack card can be used with a 2 x 10G subcard. The two stack interfaces on the stack card occupy 20 Gbit/s bandwidth, and the 2 x 10G subcard occupies 20 Gbit/s. A stack subcard cannot be used with a 4 x GE subcard. The GE interfaces on the 4 x GE subcard are actually 10GE interfaces with their rates limited, so the actual bandwidth of the subcard is 4x10 Gbit/s. This subcard occupies all the 4x10 Gbit/s bandwidth of the chip, and thus there is no available bandwidth for the stack card.