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Use a router as an AP?

Discussion in 'General Discussion' started by d-b, Dec 29, 2007.

  1. d-b

    d-b Network Guru Member

    I have a WRT54GS. I _don't_ want the routing capabilities of it, that is, I want to use it as a wireless switch/AP. Are there any firmwares that supports this?

    The reason for this is that I have another wired router X that is "in front" of my WRT, I just want the add wireless capacity to the network X "creates".
     
  2. HennieM

    HennieM Network Guru Member

    Your WRT already is an AP. Just dont plug anything into the WAN port. If your (custom) firmware allows it, you can also turn the WAN port into yet another LAN port (to give you 5 LAN ports).
     
  3. Disman_ca

    Disman_ca Super Moderator Staff Member Member

    And don't forget to disable the DCHP server on it as well.
     
  4. d-b

    d-b Network Guru Member

    Your suggestions doesn't work because the WRT doesn't bridge DHCP traffic. I basically want to turn it into a non-intelligent wireless switch/hub.

    My ISP provides me with more than one public IP (I pay extra for this), hence I don't need the NAT/DHCP functionality of my router.
     
  5. HennieM

    HennieM Network Guru Member

    You obviously have not set up everything correctly. BTW, there's no such thing as a non-intelligent wireless switch - all wireless APs MUST have some intelligence or they would not be able to connect wireless clients to a network. A WRT is just such an AP, with a few routing capabilities added.

    So much for preaching...

    The DHCP server on the WRT must be off, although DHCP server on/off has nothing to do with being an AP, a router, or anything else.... (Also set the WRT as router [not gateway] to turn off NAT, although this should not be necessary).

    Make sure your IP setup, netmask, etc. on the WRT is correct, specifically the default gateway (so the WRT does not think it itself is the gateway).
    The WRT has not, by default, got a DHCP client, hence it cannot get a DHCP supplied address itself. It must have a fixed IP address. However, any wired/wireless clients connected to that WRT will get IPs assigned from your "main" DHCP server.

    I have 11 WRTs functioning as APs, passing DHCP (and any other traffic) through mightily happy...
     
  6. d-b

    d-b Network Guru Member

    I was assisted by the Linksys support when I setup the router and they couldn't make it work either so I don't think the problem is on my side.

    The problem is, as far as I understand it, that the router "steals" one IP and not supports "bridge mode".

    > Make sure your IP setup, netmask, etc. on the WRT is correct, specifically the default
    > gateway (so the WRT does not think it itself is the gateway).

    This is exactly what I am talking about: why should I need to setup this when I just want the router to act like a wired switch/hub? I understand that some "intelligence" is required for the wireless traffic but if I (this is hyphothetic) only use the wired part of the WRT, why do I need to provide network settings etc? A wired hub/switch wouldn't require me to do this.

    > The WRT has not, by default, got a DHCP client, hence it cannot get a DHCP supplied
    > address itself. It must have a fixed IP address. However, any wired/wireless clients
    > connected to that WRT will get IPs assigned from your "main" DHCP server.

    No they don't. Linksys support tried to achieve exactly this behaviour but failed.

    I can make a backup of my config and then let you log in on my router. Send me a PM for details if you want to try this.
     
  7. d-b

    d-b Network Guru Member

    Btw, what is the difference between a WRT and a WAP in this context?
     
  8. HennieM

    HennieM Network Guru Member

    Starting from the back. In this situation, a WRT is just a WAP with 4 LAN ports. However, the stock firmware on a WRT is much less feature rich than a WAP's i.t.o. wireless setups (but 3rd party firmware gives you more wireless than a WAP's stock firmware).

    Your WRT is an intelligent switch. All intelligent switches must have an IP if you want to configure or poll or talk to that switch.

    However, if you want to treat it as a dumb switch, you can give it any IP you wish. If you don't want the WRT to use an IP on your subnet, give it an IP on another subnet; i.e.
    Say you use network 192.168.1.0/255.255.255.0. Your WRT, in default config, would have IP address 192.168.1.1, while your other devices on the network would be 192.168.1.2, 192.168.1.3,...., 192.168.1.254. Now go to http://192.168.1.1/ and then, AFTER you have turned off the DHCP server, set to router mode, configured the wireless, etc., change the IP address of the WRT to 10.0.0.1.
    Now you can use 192.168.1.1 for something else, and your WRT will just switch whatever is plugged into the LAN ports. The wireless might also work if that was setup correctly. However, you will not be able to "get into" the WRT if you want to make a change to its configuration, and you'll have to reset to defaults if you want to get into the WRT again.

    Why would you want this? If it's a big deal that WRT uses one IP, just reserve that IP on your existing non-WRT DHCP server. Alternatively give your WRT an IP outside of the already configured range of your DHCP server.

    If your DHCP server, whatever it is, and whatever machine it is running on, is worth its salt, it should anyway ping an IP address before it dishes that IP out. So, even if your WRT's IP is not reserved on your DHCP server, it should not assign that IP to any other device. (As mentioned, if your DHCP server is proper and setup properly.

    I strongly advise against the IP-out-of-subnet setup mentioned above, as it sounds like you want to have wireless. For wireless, you'll have to make changes or troubleshoot from time to time, and if you can't get into the WRT.....

    Understand this: Wireless is NOT = normal cable network hardware stuff
    Wireless = normal cable hardware stuff + Wireless intelligence
    That's why Windows for example, has an additional piece of software (additional to the network card/adapter driver), called Wireless Zero Config. If your wireless uses WPA or any sort of encryption, and additional piece of software called a supplicant is required. The same is true for the wireless AP - it needs some intelligent software to be running in order to make the wireless work.

    Bottom line, if you want wireless, you cannot have
    Therefore, to get an IP to your wireless card/adapter, you must first get it associated to the wireless network. Once this is established, your DHCP client on the PC can ask for an IP.

    In line with this, I don't understand why your WRT would not pass though DHCP traffic, except if you have it configured or connected incorrectly, or, for wireless clients, you are not associated to the wireless network for starters.

    If you get a WAP, you'll probably be in the exact same situation as with a WRT, with the added constraint that you don't have any spare LAN ports. I'm not sure if a WAP can get an IP via DHCP though.
     
  9. d-b

    d-b Network Guru Member

    This is quite similar to my current solution where I use something like 192.168.1.1 on the router as the "inside" ip. To admin the WRT I have to change the network setup on one of my computers so that it resides on the same subnet as the WRT (e.g., ip = 192.168.1.101, subnet mask = 255.255.255.0 and router 192.168.1.1. After I am done with the administration I revert the network settings to 80.216.70.x/255.255.224.0/80.216.64.x).

    However, there is a drawback with this solution: the WRT consumes one of my public IP, an IP it has no use at all for.

    As described above I can actually get around this "no-access-to-the-router-problem" by changing my computers network settings.
    I don't administrate the DHCP server.

    Unfinished sentence?

    I think the problem with the missing routing of DHCP traffic is lack of support for RFC whatever-the-number-is.

    Would 3rd party firmware fix this?
     
  10. HennieM

    HennieM Network Guru Member

    I'll try again....
    DHCP traffic is not routed - it's the nature of DHCP. DHCP takes place BEFORE a device has an IP address in a special ethernet frame, so it cannot be routed.

    I assume, in your setup, you have something like this:

    internet--wire--some-modem/router/switch--wire--(LANport)WRT(LANport)--wire--PC (1 to 3 PCs)

    In this setup, if your DHCP server on the WRT is off, your PC(s) will get DHCP IF something to the left of the WRT acts as a DHCP server. The traffic LANport-WRT-LANport is the same as any traffic that would happen through a normal wired switch, no matter what IP address the WRT has.

    If the firewall on the WRT is on, it might block IP traffic (after DHCP has taken place) through the WRT, so make sure that (and NAT) is off.

    As for 3rd party firmware, I recommend Tomato. If you want to stay close to the stock firmware, Thibor15c. Go to the downloads section of this site to see where to get it.
     

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