Add Route at Boot Time

[Hendrickson, Kenneth]

+--------------+
|   Firewall   |
|              |     .33    .34    .35    .97
| vr0    dhcpd |      |      |      |      |      Wired Network
| 172.24.10.21 |------+------+------+------+----- 172.24.10/24
|              |
|              |       +-----------------+
| vr1          |       | Wireless Router |
| 172.24.20.1  |-------| 172.24.20.2     |        Wireless Network
|              |       |     192.168.2.1 |------- 192.168.2/24
|              |       |           dhcpd |
|              |       +-----------------+
| vr2          |
| 172.24.30.1  |--------------------------------- Future Use
|              |
|              |       +-----------------+
| vr3 dhclient |-------|   Cable Modem   |------- Internet Cloud
+--------------+       +-----------------+

Problem.  I need to manually do:
        route add -inet 192.168.2.0/24 172.24.20.2

How do I get this done automagically at boot time?
What man pages do I need to (re-)read?

Thanks,
Ken