The Cisco ASR 903 Router has six interface module slots. There are two types of interface module slots. Four slots support all of the available interface modules. The remaining two slots support only the Gigabit Ethernet and TDM Interface modules, the 10 Gigabit Ethernet modules are not supported in these slots. One of these two slots is limited to a maximum of seven Gigabit Ethernet ports with the Cisco ASR 900 Route Switch Processor (RSP1).