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Wired/Wireless Switch with dd-wrt

How to make a wired dd-wrt into a dhcp forwarding wireless switch.

These instructions assume familiarity with dd-wrt and intermediate level networking concepts.

CRITICAL: These instructions may not be correct for some versions of dd-wrt. The version I run is v24 preSP2 [Beta] Build 13064 (recommended). If your router supports this version, I highly recommend upgrading to it. In any event, you should upgrade to the latest build of dd-wrt for your preferred version because of a fairly devastating security problem discovered in 2009.

Here is what you should get:

   --------------              ----------
   | Wired DHCP |              | DD-WRT |____
   |   Router   |-----wire---->| Router |    |
   --------------              ----------  wires
                                   :         |
                               wireless      v
                                   :       dhcp
                 dhcp clients <....:      clients

If you understand that drawing, then you are half way there. If you want all connections to be wireless, then you probably are looking for how to set up a dd-wrt repeater bridge.

Note that I will refer to the Wired DHCP Router as the "DHCP router" and the DD-WRT Router as the "dd-wrt router" below. Also, we will assume that the DHCP router has a local IP address of 192.168.1.1.

Here are the steps:

  1. Unplug all ethernet ports from your dd-wrt router.
  2. Put a piece of tape over the WAN port of your dd-wrt router--you don't want to use it by mistake.
  3. In dd-wrt of your dd-wrt router go to the Basic Setup tab
    • Connection Type: Automatic Configuration - DHCP
    • Router Name: Something Clever
    • Host Name: Something Unique
    • Go back and fill in that Host Name, I wasn't kidding. You'll want it to be filled when you check your DHCP router's LAN tables.
    • Local IP Address: Something outside the range of the DHCP allocation, but on the same subnet. For example if your DHCP router is 192.168.1.1 and hands out 50 DHCP addresses from 192.168.1.101 - 150, then a good Local IP Address for your dd-wrt router might be 192.168.1.151.

      Note: This allows less configurable DHCP routers to hand out a DHCP address to the router from the allocated pool without worrying about a conflict. If you have a more configurable DHCP router, you should be able to assign this address in the static tables of the DHCP router, but I have not tested this arrangement.

    • Subnet Mask: This depends on how your DHCP router is configured, but unless you have something special going on, the mask should be 255.255.255.0.
    • Gateway: 192.168.1.1
    • Local DNS: 192.168.1.1

      Note: Most DHCP routers grab DNS server entries from the provider by default, so the DNS configuration will be forwarded to the dd-wrt router. If you have DNS problems take a look at the configuration of your DHCP router.

    • DHCP Type: DHCP Forwarder
    • DHCP Server: 192.168.1.1

      Basic-dd-wrt-Switch

  4. In dd-wrt of your dd-wrt router, go to the VLANs tab.
    • For VLAN 0, make sure all LAN ports (e.g. "1" through "4") are enabled (checked) and make sure Assigned to Bridge is "LAN". Make sure that the WAN port (e.g. "W") is NOT enabled for VLAN 0.
    • For VLAN 1, set Assigned to Bridge to "LAN".

      VLAN-dd-wrt-Switch

  5. Now, make sure your wire from your DHCP router DOES NOT run into the WAN port of your dd-wrt router but instead runs into one of the LAN ports. Let me repeat that, but this time in a special font:

    Make sure your wire from your DHCP router DOES NOT run into the WAN port of your dd-wrt router but instead runs into one of the LAN ports.

  6. Make sure any wired clients or switches that connect to your dd-wrt router run into one of the LAN ports and NOT the WAN port.
  7. Steps 5 and 6 should be easy because you never took off the tape covering the WAN port on your dd-wrt router.
  8. SPECIAL NOTES:
    1. The WAN IP of your dd-wrt router will be 0.0.0.0. Remember, it is now a client DHCP forwarder on a LAN, so the dd-wrt router does not exist on the WAN! Hence something is awry if the WAN IP of your dd-wrt router is not 0.0.0.0.
    2. If you do not assign a static IP address to your dd-wrt router from the DHCP router then your dd-wrt router will have one address on the LAN but will also think it has the address you assigned for the Local IP Address in Step 3 (e.g. 192.168.1.151). If you can not reach your dd-wrt router using the IP address assigned by the DHCP router (as reported in the DHCP tables thereon), then your dd-wrt router should be reachable at the Local IP Address that you assigned in Step 3 (e.g. 192.168.1.151).
  9. When you are all done, it won't hurt to power your dd-wrt router down, reboot your DHCP router, and then boot your dd-wrt router.