This report describes how an ISP can reduce its FIB size, and in so doing delay the time at which the ISP must upgrade its routers. The approach, called Virtual Aggregation (VA) works with existing routers. An ISP can autonomously deploy VA ? it does not need to coordinate with its neighbor ISPs. While VA results in some increased load and path latency, the increase is minimal. VA can shrink FIB size by an order of magnitude or more with very little load and latency increase. While some ISPs are overflowing their FIBs today, we believe that even ISPs that are not yet in this situation may require VA in the near future. This is because FIB size may increase dramatically as IPv4 addresses expire and the address space becomes more fragmented, as well as because IPv6 usage may increase. A prepared ISP can absorb this increase using VA.