Hello, I’ve got this router RB2011UiAS-IN + 4 APs RBOmniTikU-5HnD which works really fine covering 5GHz. However I’d like to add 2.4GHz support for my network using the same SSID. Is it possible at all if so what AP for 2.4GHZ could you recommend ?
Thx
Marcin
Indoor / outdoor any other requirements or constraints?
Generaly use of same SSID on different frequency bands doesn’t differ from using same SSID on different APs operating in same band. So if you add a 2.4GHz AP to your network the same way as the 4 APs you already have, and configure identical security parameters (e.g. WPA2, AES, same key), devices will transparently roam between both frequency bands … according to their own mobility preferences.
If I can follow up on the subject.
I have HAP AC2 and 3 HAP AC Lites, all of the have dual Wifi 2.4 and 5 GHz.
Right now I have 8 SSIDs, separate for each band and each router.
If I name all of SSIDs with same name, will clients connect to whichever has better signal?
Yes
Yes.
With a gotcha: wireless interfaces on all APs have to be members of same L2 network, being served by same gateway and same DHCP server. If they’re not, all kinds of weird things can happen. If a client sees another AP with same SSID, it assumes same L2 network and after reconnecting to a better AP it won’t re-acquire network configuration (which helps mobility a lot). If the other AP is not actually member of same L2 network, old network configuration (retained by client) is not valid any more.
Specifically: the 3 hAP ac lites have to be in switching mode (not in routing mode) - so switching between wlan and upstream ethernet interfaces. And the hAP ac2 has to bridge wlan and LAN ethernet interfaces. If lites are routing between wlan and ethernet or hAP ac2 is routing between wireless and wired, then the setup is not ready for single SSID.
best is to have it outdoor but indoor can also fits fine
Thx
Right now they are all in switching mode, serving as APs, hAP AC2 is performing all the routing and serving as DHCP.
Can I at least separate each hAP lite to a different subnet and use same SSID for all of them or it is not recommended?
No.
As I wrote: when wireless client roams to another AP with same SSID, it will not reconfigure IP settings. And if different AP is in different subnet, this will break client’s connections.
E.g.:
AP1: subnet 192.168.10.0/24, GW 192.168.10.1
AP2: subnet 192.168.20.0/24, GW 192.168.20.1
Let’s assume client first connected to AP1 … it gets IP address say 192.168.10.100 and uses gateway 192.168.10.1. Later it roams to AP2. As AP2 is serving same SSID, client will continue to use old settings. Which means it’ll try to use gateway 192.168.20.1 … which is not available in subnet of AP2. Hence any ongoing connection will stop at this moment. If client accidentally decided to renew the DHCP lease, then it would eventually get settings, fit for use on AP2, but that means another IP address which breaks all the connections. But client generally won’t try to renew DHCP lease because same SSID should mean same L2 subnet and there’s no reason for client to expect that it would get completely different IP settings if it’s staying in same L2 subnet.
For illustration: compare that to wired LAN. Let’s say you have a laptop and a really long UTP cable. When you move from one room to another, connection doesn’t break and laptop doesn’t restart DHCP process. If you trip the cable and break the connection momentarily (i.e. for less than a second), ethernet layer will resume and laptop doesn’t restart DHCP process. Only if you disconnect LAN cable for longer period of time (and possibly connect to another switch interface), L3 in laptop will notice disconnection and re-start DHCP process.
When you connect same laptop to wifi network and move to another room, wireless interface will sense another AP with same SSID … and reconnect to that AP. The connection will break momentarily, but break time will be short enough that L3 in laptop will not notice it and DHCP process will not re-start. If you move far from last AP with same SSID, wireless interface in laptop might start connection to another SSID and when it connects it will signal L3 to re-start DHCP process.
Is there any reason to split wifi coverage to different subnets? And hide that from devices?
Thank you for very detailed explanation and great example, it was clear at the first line “when wireless client roams to another AP with same SSID, it will not reconfigure IP settings. And if different AP is in different subnet, this will break client’s connections” 
Currently hAP AC2 is serving as DHCP (192.168.88.0/24), 3 hAP AC Lites are connected each to one of ethernet ports of hAP AC2.
Each hAP AC Lite is in separate apartment, wifi SSID for each apartment is different (sharing same password).
Reason why I would like to separate VLANs is to easily determine from which apartment user is connected based on the IP address it got from DHCP server.
Which as you wrote won’t be possible if I want to use same SSID.
Is it possible to have 3 DHCP servers assigned to each ethernet port and thus to each hAP AC Lite, addresses would be from same subnet 192.168.88.0/24
but each DHCP would assign only partial range of IP addresses from 192.168.88.0/24?
For example:
eth1 - DHCP1 - range 192.168.88.10 - 192.168.88.100
eth2 - DHCP2 - range 192.168.88.101 - 192.168.88.200
eth3 - DHCP3 - range 192.168.88.201 - 192.168.88.250
if that’s possible then same SSID for all wifi’s can be used as well?
DHCP is basically an L2 service and there can only be one DHCP server (well, there can be multiple for redundancy, but their lease state should better be synchronized).
But then … seamless client mobility doesn’t go with ability to locate client based on IP address. Even if it was possible to assign IP address based on port identity, it would only tell you which AP was used by client to register to the network. After client roamed around, that information would be void.
Here’s possibility: create many virtual APs on every physical AP, one SSID per apartment. Use VLANs to merge SSIDs from different APs and to separate clients from different SSIDs. Each VLAN is different IP subnet served by separate DHCP servers. Having all SSIDs on multiple APs allows client roaming (for better service). And all VLANs come together in hAP ac2 which actually runs all the DHCP servers. You can configure firewall to block inter-VLAN connections thus protecting tennants of different appartments from each other.
Then look at the sxt 2 https://mikrotik.com/product/RBSXTG-2HnDr2-168
Will definitely try thanks once again
Thank you