Chained infrastructure

RouterOS General
1

Hello all,

I’m new to routerOS so I need a small help here.
I was given a bunch of old but unused RB751 devices to build a network inside a building of our community theatre. To use existing cabling I would like to keep “chained” structure like it is shown on simplified diagram below.

I need to have three VLANs which should be available on wirelless based on different SSID and two of these VLANs should be available on physical ports too (there will be 3 free ports on each device with such configuration).

I would like to know:

  • Is it possible with these devices?
  • If yes, what would be the best approach to get best performance?
  • Obviously one of the devices should act as a router, is RB751 powerful enough? there would be max 100 clients
  • Can one of the VLANs have increased (absolute) priority?
  • Can I use NV2 if there is a problem with interferences?


         w1,w2,w3       w1,w2,w3       w1,w2,w3       w1,w2,w3
         -------        -------        -------        -------      
        |       |      |       |      |       |      |       |     
INET -- | RB751 |  --- | RB751 |  --- | RB751 |  --- | RB751 | ---
        |       |      |       |      |       |      |       |     
         -------        -------        -------        -------      
         vl1,vl2        vl1,vl2        vl1,vl2        vl1,vl2

best regards
Jan

2
  • Yes, any Mikrotik AP with at least two wired ports is capable of doing this. The only real question is the level of performance possible to get and that depends on devices’ HW capacity.
  • VLAN configuration should definitely be done using switch chip capabilities as this part of manual describes it. Depending on particular type of RB751 (U or G?) the wired connection between the units might be the bottleneck on the left side of your topology sketch..
  • I’d take a device with more powerful CPU to do the routing, the venerable RB751 might not be up to the task. A very decent device might be hAP ac².
  • depends where you want to proritize traffic. It is possible to do it on router. I don’t think you can do it on APs (neither on wired nor on wireless part if these are as transparent as it gets … I guess you’d like them transparent).
  • NV2 is Mikrotik proprietary protocol (replacing 802.11), intended for point-to-point (or point-to-multi-point) wireless connections. Normal wireless client devices (smart phones, IoT gadgets, …) don’t understand it so I guess it won’t help.
3

Thanks for clear answers.
I think I understand how to configure VLANs using the switch. I expect that for passing the VLANs to wirelles I need to bridge virtual wlan with hw bridge from th switch, am I right?
Also thanks for clarification about NV2, I thought that it works in situation when the enviroment is too noisy to help APs to synchronize.

br
Jan

4

Actually you need bridge if you want to span your LAN segment to anything but wired ethernet ports. And (if configuration doesn’t abuse inconsistencies in ROS) you need bridge also for higher-layer stuff (e.g. IP for management access) whenever device switches/bridges multiple ethernet ports.

Let’s say you will be using all 5 ethernet ports in (VLAN-aware) switched configuration. Which means you’ll make all 5 ports members of a bridge, but you won’t configure anything about VLANs on bridge (you’ll do it directly on switch chip for ethernet ports). The bridge will thus be something like dumb switch (most of them are capable to transmit packets slightly larger than 1500 bytes which means that they will pass VLAN-tagged packets just fine … only they won’t give a s***t about VLAN tags).
Next step is to add any wireless interface to the same bridge (either real or virtual) but you’ll have to configure proper VLAN settings on those interfaces because bridge won’t do it for you. Something like this:

/interface wireless
set [ find name="guest_wifi" ] vlan-mode=use-tag vlan-id=666

If you want to run some SSID via “native” (read: untagged) VLAN, then you don’t set anything about VLAN on corresponding wireless interface.

If you want to have management access to such device via untagged, then the IP address should be set directly on bridge interface. If, OTOH, you want to have dedicated management VLAN, you have to create a vlan interface (with appropriate VLAN ID set) on bridge and use that interface for IP addressing:

/interface vlan
add interface=bridge name=vlanMGMT vlan-id=42
/ip address
add interface=vlanMGMT address=<mgmt IP address of this unit>
5

Ok, thanks. I will try it. Can I also do some throughput measurements using RouterOS?

6

If you’re going to do throughput measurements, stay away from (ROS built-in) bandwidth test, it’s a CPU hog and doesn’t show real life performance. Use a couple of laptops running iperf, possibly using multiple parallel streams …