Networking – Linksys wrt54gl with Tomato running in client-mode not connecting to Cisco E4200

Conduct an environmental scan, you may be getting stomped by a nearby N-router, which gladly can destroy your connection. A neighbor probably upgraded to N since you had the buffalo router.

You are running tomato, so check your power settings. You might have a weak signal and you can test this by moving right next to your router, and then increasing the gain.

Also check the physical condition of your antennas, verifing that they are screwed in well.

Had the exact situation like you, except for the gateway (Cisco RV042G). However, my solution probably won't work on E4200 due to missing features. If it is possible by using other methods, then it is beyond my knowledge. I'm adding the answer for others that may be looking for a solution like this.

Let's assume that 10.0.0.0/24 is your main network with the gateway address 10.0.0.1 and 10.0.1.0/24 is the guest network. Steps for reproducing my solution:

• Create a different subnet for the guests on the gateway. The gateway must support this feature as it creates multiple NAT tables for routing the Internet traffic to the appropriate subnet.
• Add a firewall rule for blocking all traffic from 10.0.1.0/24 to 10.0.0.0/24 on the gateway.
• Use an OpenWrt build with kernel 2.6+. brcm-2.4 builds won't due to lack of ebtables support. I used a 12.06 build with a config based onto the default brcm47xx config. With the default image opkg fails to work while I didn't try 10.03. I do recommend a Debian 7 i386 for buildroot as it wasted enough hours of my life with amd64 and various random compile errors. You may use the ImageBuilder, I think, but I didn't try it. For ebtables you need the following packages: ebtables, ebtables-utils, kmod-ebtables-ipv4. The kernel module isn't automatically added as dependency, so be careful.
• These ebtables rules from below in /etc/firewall.user for blocking the DHCP broadcast from the gateway, if gateway doesn't support multiple DHCP pools. RV042G doesn't. Found them on the OpenWrt forums, adapted them for 12.06 which uses eth0.0 as interface name for the lan VLAN.

ebtables -F

ebtables -A INPUT --in-interface eth0.0 --protocol ipv4 --ip-protocol udp --ip-source-port 67:68 -j DROP

ebtables -A INPUT --in-interface eth0.0 --protocol ipv4 --ip-protocol udp --ip-destination-port 67:68 -j DROP

ebtables -A FORWARD --in-interface eth0.0 --protocol ipv4 --ip-protocol udp --ip-destination-port 67:68 -j DROP

ebtables -A FORWARD --in-interface eth0.0 --protocol ipv4 --ip-protocol udp --ip-source-port 67:68 -j DROP

• Optional: Configure the lan interface for the secondary subnet. You need to change the address if both the gateway and the OpenWrt AP use the defaults (192.168.1.1).

config interface lan

option type bridge

option ifname "eth0.0"

option proto static

option ipaddr 10.0.1.2

option netmask 255.255.255.0

option gateway 10.0.1.1

option dns "8.8.8.8 8.8.4.4"

• Tell the DHCP server which gateway to broadcast as it would normally use the ipaddr from the lan interface config:

config dhcp lan

option interface lan

option start 100

option limit 100

option leasetime 1h

list 'dhcp_option' '3,10.0.1.1'

• Configure the wireless as a regular access point. Optional: encryption (recommended), client isolation (also recommended).

I found only one issue with this setup: a guest can still enter your main network if the subnet for that network is "guessed" and the network configuration is done manually for the wireless interface. Given the fact that the guests still see the arp broadcasts from the main network, it isn't that difficult for people that understand the previous statement. I think it can be fixed with some firewall rules onto the OpenWrt AP, but I have to research that part.