Take the 2-minute tour ×
Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

At a location with limited cabling, I've had to set up WiFi signal extenders to cover the whole area. Here is a crude diagram...

Internet - WiFi/Gateway - Extender 1 - Extender 2
                |                          |
          PC (ethernet)               WiFi device

I was able to successfully daisy-chain three together, and I can access the internet from WiFi devices connected to the farthest extender. Is this a supported configuration? If not, what kind of issues can arise from it? The reason why I ask is that the PC keeps reporting IP address conflicts, and I'm wondering if that's caused because of the way this is configured.

Additionally, I noticed that the extenders named their own SSID similar to the one they are connected to, but with a suffix. Would there be any issue in naming them all with the same SSID, to enable seamless roaming as you would with multiple standalone APs?

share|improve this question
3  
Why not just add APs? Why use Extenders? –  Chris S Dec 12 '12 at 20:43
    
What wifi extenders are you using? –  Matt Dec 12 '12 at 20:43
    
You can add other APs in transparent bridge mode. Or use WDS. –  Matt Dec 12 '12 at 20:43
    
Extenders are presumably cheaper, and were already available at the site. I had to rejigger them after the main WiFi device was replaced. –  Bigbio2002 Dec 12 '12 at 20:46

3 Answers 3

up vote 5 down vote accepted

Extenders typically are nothing but Wireless Access Points - with two radios if they are any good. The difference to a "classical" access point configuration would be that their upstream link is wireless - similar (but not necessarily identical) to the Universal Repeater Mode. Under performance and reliability considerations, an access point should be connected upstream by a wired link. Where this is not possible and if your requirements permit it, you can do a radio-to-radio forwarding by the means of "extenders".

As each extender creates an own collision domain, you could daisy-chain them indefinitely - pretty much as you could do with wired switches. Obviously, round-trip times would increase for the connected clients as each hop would add to latency. The address conflicts reported by the host may be arising from either a true address conflict (something is claiming the IP address the host wants to use and responding to ARP who-has requests) or a network loop where the ARP request from the host would be reflected back to it, answered and the answer reflected back as well - which would look like another host is claiming the address, while in fact it would just be a looped back transmission.

Whether or not your extenders would have any issues with setting the extended network's SSID to the value of the uplink's SSID would be implementation-dependent. Basically, the extender has to be smart enough not to try to connect to itself or any of its downlinks (so it needs to have some idea about the topology) for this to work.

As the wireless infrastructure set up in this way is a pain in the arm to manage - especially when you are changing the PSKs of your wireless networks (it looks like you are using PSKs, so you must be changing them frequently, right?), you seriously should be looking into vendor-specific WDS systems where you would not need to touch every single device in the right order to get your keys changed without interrupting connectivity for your management data path.

share|improve this answer

You don't want to do this. Since you're not using WDS, the extenders have to impersonate their clients.

A WiFi access point will not bridge to a WiFi client. If you don't set up WDS, each repeater is a client of the upstream access point. The upstream access point will only send packets addressed to its clients over a client link, and clients of the repeater are not clients of the upstream access point, so it will not send their packets to the downstream access point. To get around this, extenders impersonate their clients.

This creates all kinds of problems. Among other things, it prohibits seamless roaming because the real client would conflict with the impersonated client.

Your choices that actually work reliably are either WDS or wiring the access points together.

share|improve this answer

I think the key is figuring out the ip that the second extender is using and excluding it from the ip pool of your dhcp server. The second extender will take its own ip address but won't show up as a "connected" device on the dhcp server.....because it's not really connected to it, but to the first extender....but it will have an ip....another device connected to the router could lease that same ip and cause mayhem.

share|improve this answer

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.