BGP is not supported in all IOS feature sets, you'll need a feature set that supports BGP (for 12.3 starting from SP feature set and your image is IP Base and thats why it doesn't support BGP). Please use Cisco Feature Navigator to find information about your platform and the supported Cisco IOS software image with your required features:
Introduction: The "external-out enable" command is available for
configuration under the "router ospf process" in case of the IOS-XR
operating system. This command basically enables advertisement of
intra-area routes on the device as external routes in th...
Introduction Basic configuration for netflow Scale parameters for
netflow Netflow support Architecture Packet flow for netflow Inside the
LC CPU Netflow Cache size, maintenance and memory Sample usage Cache
Size Aging Permanent cache Characteristics Which...