Cisco Gigabit Switch Router 12008 Installation And Configuration Manual page 46

Overview of the Cisco 12008
Although you can install a line card in slot 0, the recommended convention is for the RP
to occupy this slot.
Figure 1-8
Upper
card
cage
A minimally configured Cisco 12008 contains the following cards in the upper card cage:
•
One RP
•
One CSC
•
One Cisco 12000 series line card of any type
1-24
Cisco 12008 Gigabit Switch Router Installation and Configuration Guide
Upper Card Cage of the Cisco 12008 Router