Dual SSID one for public network
From DD-WRT Wiki
This worked for me on V24 release with wrt54GL
My main network is 192.168.1.1
1) Wireless -->basic setting added another Interface, unbrigged, and with IP of 192.168.2.1, mask of 255.255.255.0
2) In wireless security, configure the security for the second adapter.
Apply changes.
3)Setup - networking --> dhcpD add another DHCP server for the second interface choose wl0.1. In my case it was 192.168.2.10 5 users
4) Administration---> commands
iptables -I INPUT -i wl0.1 -p icmp -j ACCEPT
iptables -I INPUT -i wl0.1 -p tcp --dport 23 -j logdrop
iptables -I INPUT -i wl0.1 -p tcp --dport 80 -j logdrop
iptables -I FORWARD -i wl0.1 -o br0 -j logdrop
Save firewall
5)Reboot router
That's it