Many of the routers on the market support third-party router firmware like DD-WRT or OpenWRT. These firmware add additional functionalities to you router if your network is more complex than a single flat network. It also allow you to tinker with many advance settings to customize for your needs.
One such usage is to use DD-WRT to create multiple VLANs and link them together. This was done for a client when they have 3 VLANs from a legacy setup, but needed each VLAN to talk to each other. I know it does seem counter intuitive since the usage of VLANs is to segregate your network into different segments, but for the case reverse engineering it allows 3 separate networks to talk to each other.
I assume you already have already installed DD-WRT on your router. If not, you can read my guide here on how to do so.