Suppose we have an access point capable of multiple SSID and VLAN. We want to set up an open hotspot for public access on one channel, and a secured channel for staff. For this exercise, we will use a Ubiquiti Unifi AP and set up two WLANs. The first WLAN will be called “Public” and be assigned to VLAN ID 20. The second WLAN will be called “Secured” and be assigned to VLAN ID 10. Our basic diagram looks something like this:

The general idea will be to create a VLAN trunk between the AP and the Mikrotik router to pass traffic for both VLANs. In addition, the Unifi AP will be in it’s own subnet for management purposes and needs to be untagged (not assigned to a VLAN). The “Public” WLAN will be given it’s own subnet and will pass through a hotspot configured on the Mikrotik, while the “Secured” WLAN will be part of the regular wired LAN.

The Unifi AP is already configured with the two WLANs / VLANs, is adopted by a controller at the default address (http://unifi:8080/inform ), and has a static IP of 192.168.250.199.
If we are not running a DNS server of our own, we can tell the AP to use the Mikrotik router’s IP (192.168.88.1) for DNS and then insert a static entry to forward requests to the appropriate:
[sourcecode language=”plain”]
/ip dns static
add address=1.1.1.1 disabled=yes name=unifi ttl=1d
[/sourcecode]
Obviously, change 1.1.1.1 to your controller’s IP address.

Next, let’s use port 5 of the router and construct a trunk for both VLANs and the untagged management subnet of the AP. We need to un-assign the master port option for port 5 if it is set as a slave to another port. The name of the interface has been set to ‘ether5-vlan-wireless’. We create our two VLANs:

[sourcecode language=”plain”]
/interface vlan
add arp=enabled disabled=no interface=ether5-vlan-wireless l2mtu=1594 mtu=\
1500 name=vlan10secured use-service-tag=no vlan-id=10
add arp=enabled disabled=no interface=ether5-vlan-wireless l2mtu=1594 mtu=\
1500 name=vlan20public use-service-tag=no vlan-id=20
[/sourcecode]

Now, what we want to do is create a bridge which will include both port 2 (regular LAN / wired clients) and VLAN10 (secured wireless). We need to then assign / move the DHCP server that was running on port 2 to the bridge. First, create the bridge:

[sourcecode language=”plain”]
add admin-mac=00:00:00:00:00:00 ageing-time=5m arp=enabled auto-mac=yes \
disabled=no forward-delay=15s l2mtu=1594 max-message-age=20s mtu=1500 \
name=bridge1 priority=0x8000 protocol-mode=none transmit-hold-count=6
[/sourcecode]

Now, assign both port 2 and vlan10 to the bridge:

[sourcecode language=”plain”]
/interface bridge port
add bridge=bridge1 disabled=no edge=auto external-fdb=auto horizon=none \
interface=vlan10secured path-cost=10 point-to-point=auto priority=0x80
add bridge=bridge1 disabled=no edge=auto external-fdb=auto horizon=none \
interface=ether2-master-local path-cost=10 point-to-point=auto priority=\
0x80
[/sourcecode]

In my case, I prefer to assign IP addresses to secured wireless machines via the alternate configuration tab in Windows TCP/IP settings. But for this to work, the wireless client must not see any DHCP services running on the secured WLAN it is connecting to. So, we create a bridge filter rule to block DHCP on VLAN10:

[sourcecode language=”plain”]
/interface bridge settings
set use-ip-firewall=yes
/interface bridge filter
add action=drop chain=input disabled=no in-interface=vlan10secured \
ip-protocol=udp mac-protocol=ip src-port=67-68
[/sourcecode]

Notice the first line that tells the bridge to use firewall rules. Very important!

As for IP addresses on the local interfaces, we have the following:
[sourcecode language=”plain”]
/ip address
add address=192.168.88.1/24 comment="default configuration" disabled=no \
interface=ether2-master-local network=192.168.88.0
add address=192.168.151.1/24 disabled=no interface=vlan20public network=\
192.168.151.0
add address=192.168.250.1/24 disabled=no interface=ether5-vlan-wireless \
network=192.168.250.0
[/sourcecode]
These addresses are for the normal LAN (192.168.88.0/24), the public wireless (192.168.151.0/24), and the Unifi management subnet (192.168.250.0/24). The Unifi needs an untagged or non-vlan path to communicate with a controller. If we didn’t care about the AP communicating with a controller, we could drop the IP assignment for the physical port 5. Please note that if you are using ‘guest portal’ on the Unifi, you need the controller.

Now, we move or create a DHCP service for the bridge interface and VLAN20:
[sourcecode language=”plain”]
/ip dhcp-server
add address-pool=default-dhcp authoritative=after-2sec-delay bootp-support=\
static disabled=no interface=bridge1 lease-time=3d name=default
add address-pool=vlan20public authoritative=after-2sec-delay bootp-support=\
static disabled=no interface=vlan20public lease-time=3d name=vlan20public
/ip dhcp-server network
add address=192.168.88.0/24 comment="default configuration" dhcp-option="" \
dns-server=192.168.88.1 gateway=192.168.88.1 ntp-server="" wins-server=""
add address=192.168.151.0/24 comment=vlan20public dhcp-option="" dns-server=\
"" gateway=192.168.151.1 ntp-server="" wins-server=""
[/sourcecode]

A little explanation may be in order in regards to the DHCP stuff. The service needs to run on the bridge interface, and will not work on a port assigned to a bridge. So, if we have the default DHCP server going on the default port 2, and then move port 2 into a bridge, DHCP stops. Furthermore, being as the DHCP service is now on the bridge, it will also hand out leases to the wireless clients on VLAN10 as well as port 2, and whatever other ports might be slaved to port2. Again, in my case, I didn’t want DHCP running across the VLAN10 interface, so it was blocked by filter rules.

As for the hotspot service, we need to run it on the VLAN20 interface:
[sourcecode language=”plain”]
/ip hotspot
add disabled=no idle-timeout=none interface=vlan20public keepalive-timeout=\
/ip hotspot profile
set [ find default=yes ] dns-name=spot.hot hotspot-address=192.168.151.1 \
[/sourcecode]
This is just a snippet for the hotspot, but the main thing to take away is that the interface needs to be the VLAN interface, not the physical port.

Let’s not forget to block traffic between our public and internal networks, and also block public traffic to the AP management subnet:
[sourcecode language=”plain”]
/ip firewall filter
add action=drop chain=input disabled=no dst-address=192.168.88.0/24 \
src-address=192.168.151.0/24
add action=drop chain=input disabled=no dst-address=192.168.250.0/24 \
src-address=192.168.151.0/24
[/sourcecode]

Mikrotik VLAN Trunk and Unifi AP
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