BGP Aggregation

When I follow the example of the BGP Case study in the wiki for a very simple aggregate, the bgp seems to continually reset. I have 2.9.34 with routing test.

I have 5 BGP peers which announce to me c classes of the supersubnet 10.0.0.0/8
What I want to do is to aggregate a few c classes to a subnet lets say 10.21.0.0/16

Can somebody help me with this… ?

I think that the command is right…

add prefix=10.21.0.0/16 summary-only=yes inherit-attributes=yes attribute-filter="" \
    suppress-filter="" advertise-filter="" instance=default disabled=yes

On the other hand I keep getting BGP resets…. Some examples? Something with filters as well? Am I doing something wrong?