Internet2's R&E network (AS11537) will accept up to IPv4 /27 and IPv6 /49 prefix lengths from both participants and peers.  While routes matching the above restrictions will be advertised to BGP neighbors of Internet2, it is up to each network to decide the maximum prefix length they will accept. Some networks may have more concervative limits than Internet2 R&E.

Internet2's I2PX network (AS11164) will accept up to IPv4 /24 and IPv6 /48 prefix lengths from both participants and peers.  These prefix lengths are typically what is also accepted by the commercial networks that I2PX peers with.