Advertising rented IPv4 prefix from a different ASN.

[Andrew <andrew () vianet ca>]

Hello List,

I work for a medium sized ISP.  We are entering an agreement to rent 
some IPv4 space from a local higher education institution.  Being a 
multi-homed ISP we would like to advertise the rented prefix from our 
ASN.  The prefix that will be advertised is a smaller subnet from the 
higher educations block; they will continue to advertise the larger 
prefix.

What is the best way to accomplish this?  Is there any way of doing this 
without having to tunnel the traffic through the origin ASN?

I feel if we just adverse the prefix it get put on a bogon list for 
prefix hijacking.  This space is rented long term but they are not 
interested in reassigning the space to us.  They also want to keep 
advertising their prefix as one contiguous block.

I appreciate any insight and information.
Thank you for your time,
Andrew.