Guest network subnets on multiple APs

Hi all,

I suppose I have a general question about running a guest network on OpenWrt devices.

I'm currently following this guide to create separate guest WLANs on my APs: https://openwrt.org/docs/guide-user/network/wifi/guestwifi/guestwifi_dumbap

However, the guide does not explain how multiple APs with guest networks should be treated. Assumed I have 3 APs with non-overlapping ranges, but use the same SSID for guests, should all APs have their guest interface created on the same subnet or different ones?

Since each AP will act as a DHCP server, could this be a cause for IP conflicts if two guests enter different APs' ranges and get assigned the same IP or would DHCP just switch them to new addresses if they enter the other one's range?

The best way to handle this situation is to setup a guest vlan on your main router, and then pass your networks via a trunk to all of the APs. If your main router doesn’t have vlan functionality, you could theoretically setup one ap with the guest network routed, and then make a trunk port from there to feed the other APs.

Having each ap run its own guest network will not be a very good experience - each time a client roams from one ap to another, it will need to get a new dhcp lease, which may be different from the previous one and this may interrupt the connectivity for those guest client devices.

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Hi psherman,

thanks, yes, defining a separate VLAN would be the optimal solution, but there's an unmanaged switch in the way, so I had already crossed that option off in my mind.

I suppose unless we buy new hardware, there is no way to supply the tagged connection around that?

I guess it would be most important that the internal network is stable, which is handled by the main router anyway. What would be the worst consequence? Just a short connection loss for guests while in transit from one AP to another?

Depending on the requirements here (number of ports, PoE, etc.), you can get relatively inexpensive smart/managed switches these days. Obviously this depends on your local market, too. But entry level 5-port smart switches can be purchased for ~$30 US. Also, all-in-one router devices that run OpenWrt can, more often than not, also function as managed switches.

This depends...

  • If the wifi is well tuned and the guests aren't likely to experience roaming when stationary (or relatively so), maybe it is okay. But if the setup isn't optimized, even a device that is not moving at all could find itself bouncing between multiple APs.
  • Also, it is very much dependent on the things that the guests are doing. web browsing, email, and text messaging services are typically very tolerant of momentary breaks in connectivity. Gaming, video chat, and streaming media don't typically like interruptions of any significant length.