there are various ways to inject a route into BGP.
either you have a route in your routing table that you can advertise via the "network x.x.x.x mask y.y.y.y" command. If that route is not available, then yes, using the static route to null puts that network in your routing table that allows for the network command under router BGP to pick it up.
You could also redistribute static, once you have that configured, but that "tags" the route as "incomplete" in eBGP terminology, which gneerally is not even an issue btw.
another option is to advertise an atomic aggregate, once you have PART of that netowkr in your routing table of some sort, you can use the summary address option to advertise a larger subnet.
Now just to note, generally eBGP peering SP's will validate and filter your routing updates to make sure what you advertise is what belongs to you.
IF this is just within your own AS, then there is no issue of course as you have full administrative control over what you advertise and how.
regards!
xander
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Xander Thuijs CCIE #6775
Principal Engineer IOS-XR/XR routing
