Consider the forwarding table of an IP router. Each entry consists of an IP prefix and the corresponding next-hop router for packets whose destination address matches that prefix. In a prefix \(/N\), the most significant \(N\) bits of the subnet mask are set to \(1\).
| IP prefix | Next hop |
|---|
| 10.1.1.0/24 | R1 |
| 10.1.1.128/25 | R2 |
| 10.1.1.64/26 | R3 |
| 10.1.1.192/26 | R4 |
The router forwards 20 packets to each of the following five hosts:
| Host | IP address |
|---|
| 1 | 10.1.1.16 |
| 2 | 10.1.1.72 |
| 3 | 10.1.1.132 |
| 4 | 10.1.1.191 |
| 5 | 10.1.1.205 |
The number of packets forwarded via next-hop router R2 is ________.