WikiDevi.Wi-Cat.RU:DD-WRT/VLAN Configuration

First aid:

There is a command for configuring VLANs in busybox: vconfig

BusyBox v1.00 (2005.04.16-19:38+0000) multi-call binary Usage: vconfig COMMAND [OPTIONS] ... vconfig lets you create and remove virtual ethernet devices. Options: add            [interface-name] [vlan_id] rem            [vlan-name] set_flag       [interface-name] [flag-num]       [0 | 1] set_egress_map [vlan-name]      [skb_priority]   [vlan_qos] set_ingress_map [vlan-name]     [skb_priority]   [vlan_qos] set_name_type  [name-type]

Easy step-by-step instructions for putting port 4 on it's own subnet using VLANs can be found at Linksysinfo and Geek Pages