Cisco C3KX-NM-10G Network Module – 4 x Expansion Slots
The module has four slots. Two slots support only 1-Gigabit SFP modules. Two slots support either 1-Gigabit SFP or 10-Gigabit SFP+ modules.
The four slots are grouped as two pairs, with each pair consisting of one SFP slot and one SFP+ slot. Each pair supports either two 1-Gigabit SFP modules or one 10-Gigabit SFP+ module. A 10-Gigabit SFP+ module cannot operate at the same time as the corresponding 1-Gigabit SFP module in the pair.