I'm recent to OpenWRT, though I know quite a bit about networks.
I didn't find a method to simply extend an existing WiFi network with the repeater function. "LAN interface of the relayd device MUST be on a different subnet for relayd to work" irritates me.
What I have:
The existing AP is connected via cable to a server. This server offers Internet connectivity and IP-addresses via DHCP. The existing AP has SSID 'MySID'. So far pretty much standard.
What I want:
The OpenWRT repeater (EnGenius EAP600) will sit on a fixed IP in 192.168.1.0/24; excluded from the DHCP on said server. It will receive its data via a WiFi link (2.4 GHz) from that AP, and retransmit under that same SSID of 'MySID' via 2.4 and 5 GHz. Same IP range, so that users can almost seamlessly move from one area to the other.
DHCP should come from the server mentioned above, too. Authentication will be done on either AP or repeater, same SSID, same same method, same password.
I have briefly tried on the EnGenius firmware, where this worked, since it offered a setting 'repeater'. But that firmware is old, not updated for 6 years, and pretty ugly and limited.
Can I do the same with OpenWRT?
B.A.T.M.A.N. and 802.11s meshing has its use case, but in order to use it, all participating APs need to support it, which effectively means OpenWrt devices only - at which point you could just as well use WDS/4addr instead, which would be more equivalent to the requested features of relayd done properly.
Isn't this about the same what any cheapo repeater does? You hang it into a power plug, set it to receive an existing AP, and then to re-distribute the Wifi-Signal ("Range Extender")?
Yep. Would be strange if the most advanced AP and router software with all bells and whistles wouldn't allow most basic settings.
I have tried for the last two days, as good as I could, I'm recent to OpenWRT though, without success. I could 'client' to the AP before, and 'Enable' an AP, but then one or another would go away.
wifi (sta) - wifi (AP) in a repeater mode, and wifi (sta) - ethernet in a 'downlink' mode on the same subnet is not directly supported by the 802.11 standard.
You can easily do these things in a normal routed mode (where the AP/ethernet is on a different subnet than the sta mode uplink).
But for a true 'repeater' mode, you must use something like relayd. But, these are hacks on top of the 802.11 standard that have some quirks and don't universally work (they don't support IPv6, for example).
The vendor firmware for repeaters often use some proprietary 'magic' (often using relayd under the hood and/or non-open-source code from the wifi chipset vendors) to make it transparent... but even those don't always work properly. Others may do some encapsulation between the nodes to make it work (for example, Unifi APs can do a wireless backhaul that includes all associated VLANs and can operate as an ethernet downlink, too; but these are using a proprietary method to achieve this). In general, you need to have consistency in the chipsets and/or firmware in order to do this stuff -- you may notice that many wifi repeaters are only technically compatible within a given brand/product line and may not work with other vendor's equipment).
I accept your post, with one reservation: I am a retired sys and network admin and I cannot confirm "but even those don't always work properlyt". From a silly old Fritz Repeater to a recent acquisition for 8 USD including shipping from China (only bought as client WiFi-2-RJ45), they all worked here as what I needed at times: extending the range of an IPv4 AP. This same EAP600 has been totally okay with a different AP for the last 5 years.
I do know how things are; I don't like that 'repeater' concept myself. But here I am bound to just having a power plug, and need to extend the range. The vendor firmware did just fine. WDS also has its quirks. So I was actually most happy to find OpenWRT to support this AP; and me to replace a six year old dubious firmware based on a 3-something kernel with the greatest and the latest.
The point here was that some of these devices are flaky. Even OpenWrt with relayd has known issues, including the inability to pass DHCP packets properly in some situations.
Many may work well, of course, but they often have some proprietary methods happening under the hood.
Sure... I can understand that. But your disappointment should be directed at the original 802.11 spec -- this was not a use case that was envisioned (or prioritized) at the time that it was ratified.
Good. So let's open a new path. Should I open a new topic, or can we continue here? I'll try.
So what is the suggestion of the community for the situation that I find myself in?
I need to extend a wireless network, so that users can roam from one AP to another, without being cut off, without reconnecting, same SSID, same IP, dished out from a DHCPd in front of said first AP for which the range must be extended. That first AP neither runs OpenWRT nor can it be converted to it.
and replace it with OpenWrt supported hardware, or if it is an ISP modem/AP that cannot be replaced, put it in bridge mode and treat it like a modem only device with a new OpenWrt supported hardware device for the AP, if you can.
I've found used and open box OpenWrt supported hardware on ebay to be very economical over the years.
Typical protocols for roaming are 802.11k, 802.11r, 802.11v.
I personally have never tried them though. You will likely still need to compromise. In particular: How are you going to activate and configure your first ap to use these protocols, if your first ap is not configurable? Even if you manage to set them up, for the reasons mentioned by others in this thread, they might not fulfill all your requirements. There are complex technical reasons for the way things are (right now?). E.g. just look at Mode WIFI STA bridge with LAN does not work - #11 by mk24. It's complicated.
About a year ago I replaced my last repeater with a pair of Powerline Adapters and get a reliable 200 Mbps. YMMV depending on where in the circuit these reside.
This is standard roaming behavior (and does not require 802.11 k/r/v -- those are additions to the 802.11 standars that aim to improve roaming performance, but they aren't necessary, nor are they a slam dunk).
The only thing that complicates your situation is the need to do this wirelessly. Wireless backhaul is not always easy for a variety of reasons, some of which have already been discussed. If you can run a wire (or per the suggestion from @RangerZ -- maybe powerline adapters could work for you), you would find this whole process almost trivially easy.
The following is out of scope for detailed discussion on this (OpenWrt) forum, but in general...
You can try to get an 'extender' from the same manufacturer who makes your first AP... implementations like WDS tend to only work properly/well with the same vendor providing both sides.
Or buy a commercially available 'repeater' device and see if it works (like I said, some actually do work well, some don't, and some require that they work with the same brand in order to function).
And there is always the option of replacing your first AP with one running OpenWrt.
As far as I know, all of this (except the "without reconnecting" clause) is achieved by the "relayd" configuration. A STA can be connected to only one AP at the same time, so the clients must disconnect from one AP and then connect to another one; this can be made seamlessly, but it has to be done.
Building on what @eduperez said about the disconnect/reconnect requirement, I want to point out that I glossed over this... This disconnect-reconnect cycle will necessarily happen, but at a human scale it should be (nearly) seamless if everything is tuned well, and it should certainly be automatic. Roaming is a client side process, so the APs have limited-to-no direct control over this, but there are things that can be done to improve the performance and to encourage clients to make good roaming decisions.
802.11k/v/r are intended to improve roaming by sharing information across the APs and client devices so that the re-connect phase is faster and requires fewer steps. However, these standards can be hit-or-miss, and it is sometimes worse than plain old roaming due to client device issues. As such, it is recommended to work first on creating a good traditional roaming environment and then implement these standards (if applicable to your situation) only after things are generally smooth.
Now this sounds more reasonable. 'Seamlessly' doesn't mean 'without reconnecting', naturally! So, like @psherman correctly writes, not doing any real-time stuff like audio or video conferencing while moving about, my users usually don't notice.
Just for the fun of it, I tried @RangerZ , but the wireless way: pulled a crappy TL-802N from the box, piggybacked it to the EAP600, extra USB power supply, short RJ45-cable from the TL to the EAP. Of course this works, kind of sh**y, but does.
Why can't OpenWRT do the same with a built-in radio and a single, simple software switch? Isn't a TL-802N just a normal 802.11 client and the EAP a normal AP; just in series?
Please, correct me if I'm wrong.