Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

I have a Motorola WR850G wireless router that I'm trying to use not as a typical router (DSL in, one wired and wireless home network out), but as a box that extends a subrange of my home net (192.168.1.x) to wireless clients with DHCP.

I know that a firmware like DD-WRT would likely work on this router, but before flashing DD-WRT onto the router, I would like to fully understand the original features it offers with its own firmware, version 6.1.4.

One thing I don't get:

In the LAN settings, I give the WR850G the IP 192.168.1.200 and tell it to offer DHCP addresses in the range from 192.168.1.201 to 192.168.1.254. This works. I can even ping a smartphone that got accepted via DHCP at 192.168.1.201 from another box inside of my wired home net.

Now, once I configure the WR850G as an Acess Point (the options are "Router" and "Access Point"), I lose access to the browser config interface. I know this has to happen once I give it another IP, but why does it seem to become inaccessible when it is put in the Access Point mode? Does it somehow lose its own assigned IP (192.168.1.200) when being put into this mode?

More generally put:

What does it do when I configure it as an access point, anyway? What is a wireless access point? The definition seems to be unclear.

Please excuse my noob-ness, I am still in the process of learning wireless networking, and sometimes the terminology is strange. For instance, on a wired network, a bridge is a box with two NICs, negotiating between two networks (e.g. 192.168.1.x and 10.0.0.x). On a wireless network, a bridge is something like two boxes with an antenna each, acting like a straight piece of CAT5 cable on the same subnet, without the connected boxes even noticing that they are using a piece of wireless network...

share|improve this question
    
not sure really as i have rarely used wireless, but if i recall, a device that is a Wireless Access Point, enables individual computers - called hosts to connect to it wirelessly. But not other wireless routers. A weak guess, to connect two wireless routers you need a device in between called a wireless bridge. If I recall, A Wireless router, is a wired router with wireless access point built in. I don't recall what router mode as opposed to access point mode, does. –  barlop Aug 25 '13 at 9:58
    
if this helps.. i once had a wireless usb stick, that could connect me to a wireless router, or it had an access point mode, which would mean others would connect to it. –  barlop Aug 25 '13 at 13:06
    
You did not mention what IP addressing is being picked up (by clients) when in the access point mode? If your just looking to control, this might help marasingha.blogspot.com/2006/07/… –  Psycogeek Aug 25 '13 at 14:38
1  
An access point allows wireless clients to connect to it(wirelessly). You typically connect the access point to a computer with a cable, or "home router" with a cable. It's a bit like how a wired switch doesn't necessarily need an IP. If it doesn't have an IP as an access point, then you could just reset it if you want to access the web interface mode and it won't be in access point mode. I don't recall if such things have an IP when in access point mode. –  barlop Aug 25 '13 at 16:29
    
Did you tried connecting Ethernet cable to LAN ports despite of WAN port and access the setup page. During connecting to LAN port what ip you are receiving? –  Renju Chandran chingath Mar 23 at 16:18
show 1 more comment

2 Answers

up vote 2 down vote accepted
+50

The short answer: this is by design and is expected behavior. Your router's IP address has likely changed based on the DHCP from your modem.

By changing from router to AP mode you're basically asking it only send and receive WIFI but lose all of the routing functions. Consider all of the things that your router usually does: dhcp, firewall, network routing, etc. This all gets shut off and relies on another device to provide those services.

This is helpful if you're in an environment that needs multiple places to connect to wireless (like a school or business). If you kept it in router mode you'd be segregating your network all over the place - someone on wireless router #1 couldn't automatically and easily talk to someone on wireless router #2 (without your intervention at least).

In such scenario you'd want a primary server providing your DHCP functionality and APs placed strategically within your buildings where you want wireless access. You'd connect to any of the APs (likely all the same SSID), it reaches back to your main server for DHCP information and gives your computer its IP address.


Now, from what I understand you've got a home network that you want to look like:

DSL Modem ------ Wireless Router WR850G ------ Wired Clients (192.168.1.2-199)

...................................[Wireless Clients (192.168.200-254)]........................................

If this is the case let me suggest that there isn't much point in having a split DHCP range like that if you want everything to talk together anyway. You could leave your router in router mode and make your DHCP range something like 192.168.1.50-254 and this would still give you a decent range for static IP assignments for anything like a server that will need to keep a consistent IP. This would mean that all of your connections will be going through that router, that is, you'll need to ensure all of your wired gear goes through your router's LAN ports while your DSL modem is plugged into your WAN port of the router.

Hopefully this helps - but feel free to comment to clarify anything I may have missed or assumed incorrectly about your configuration.

share|improve this answer
    
The setup is a bit different from your guess. I have a DSL modem, a router (linux box), and am trying to connect the wifi box to my internal home network (192.168.1.0/24). I agree it's best to let the linux box be the DHCP server, and I thank you for the background info. But back to the thing that got me curios in the first place: Any chance that the wifi box doesn't change its IP address when being reconfigured as AP, but loses it alltogether, becoming completely transparent - the same way a simple and cheap 5- or 8-port wired ethernet switch never has an own IP, and never had one by design? –  zebonaut Mar 30 at 8:16
    
Not impossible. One thing I'd do is a port scan of your network within your DHCP range using something like nmap and see what comes up. If that doesn't pull up anything obvious you could check out what DHCP reservations have been handed out and see if anything matches the MAC address for your AP/Router. It would make sense that you should still be able to manage your device even in AP mode so it should still be accessible. It may be a matter of you having to plug into it and set your IP address statically on your computer to be able to manage it. –  Bradley Forney Mar 30 at 16:01
add comment

The Motorola WR850G does NOT have a built-in DSL modem. Its WAN port is an Ethernet, which you could hook into a separate DSL or Cable modem. It can get is IP address from your upstream home gateway (which is probably a NAT gateway router and DHCP server in one), but it may only be able to do that over its WAN port. So configure its WAN port to get its address via DHCP, then configure it to be an AP, then connect its WAN port into your LAN.

This should allow it to get an IP address lease from your existing DHCP server on your LAN, and it should bridge packets between its WLAN, LAN, and WAN ports.

Then you should be able to reach its admin interface by pointing your browser (on any client machine on your [W]LAN) at whatever IP address your AP was given by your DHCP server. You might choose to give your AP a static IP address from within the private IP subnet that your existing home gateway router uses for your LAN. That way you'll always know what IP address it'll be using.

Regarding Ethernet and Wi-Fi network equipment terminology:

  • A box that just repeats all packets out all ports (except the one it came in on) is called a "repeater" or a "hub". The names are interchangeable in the standards documents.
  • A box that is like repeater/hub but looks at the destination Ethernet MAC address, and only transmits packets out the right port (the port where it knows that destination Ethernet MAC address lives), is called a "bridge" or a "switch". Again, these names are interchangeable in the standards docs.
  • You were mistaken to say that a box that sits between two separate IP subnets is a bridge. A box that sits between two separate IP subnets is a "router" or "gateway". Sometimes in the IP world, those two terms are used interchangeably, but in some broader networking academic literature, for it to be a true "gateway" it has to work at something higher than the IP layer; so a NAT (a.k.a. NAPT, PAT) gateway, which messes with Transport-layer TCP/UDP port numbers, deserves to be called a gateway.
  • In 802.11 (Wi-Fi), an Access Point (AP) is, at the very least, a box that bridges Ethernet-like frames between wireless clients and a wired Ethernet LAN.
  • In some contexts, people use the term "wireless bridge" to mean:

    1. A box that connects wirelessly to another wireless bridge box to connect two wired Ethernets together via a wireless link. Also known as a "Wireless Distribution System" (WDS) bridge.
    2. A box that connects a single wired Ethernet device wirelessly to an AP.

    Sometimes people are so used to using the term "wireless bridging" for these kinds of boxes that they forget that APs are technically wireless bridges as well, because they bridge between wireless clients and wired Ethernets. I should also mention that boxes that are commonly called "wireless repeaters" or "wireless range extenders" are also technically wireless bridges, because they bridge between one kind of wireless link and another.

share|improve this answer
    
Thanks for explaining the right terminology. Any chance that the wifi box doesn't change its IP address when being reconfigured as AP, but loses it alltogether, becoming completely transparent - the same way a simple and cheap 5- or 8-port wired ethernet switch never has an own IP, and never had one by design? –  zebonaut Mar 30 at 7:52
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.