Core Issue
Slot 0 of the 2801 router supports voice only and cannot be used for configuring PRI, which is used for voice and data.
Resolution
The pri-group can be configured in Slot 1, Slot 2 or Slot 3. However, you cannot install and configure the VWIC-MFT-XX card in Slot 0 of the 2801 router because this slot supports voice only. It does not support the pri-group configurations.
For more information, refer to the Installing Modules and Interface Cards section of Chassis Installation Procedures for Cisco 2800 Series Routers .