In the following diagram we want to route traffic from rui11 (10.222.222.100/24) to dhcp0 (10.99.99.3/24) via the ruirouter0 router.
+-----------------------+ +--------------------------+ +-----------------------+
| dhcp0 | | ruirouter0 | | rui11 |
+-----------------------+ +--------------------------+ +-----------------------+
| | | | | |
| 10.99.99.3/24 <-------------+ 10.99.99.101/24 | +-----+ 10.222.222.100/24 |