Mesh problem - Client cannot see all the Access points

RouterOS Wireless Networking
1

Hello everyone,

I have built a mesh network using Mikrotik routers.
I am happy because it works quite well. However, I have a problem.
I am not sure if it is due to bad configuration or just because I do not understand how the mesh network should actually work.

To begin with, the Wireless Distribution System works well.
So, all the routers have a full connectivity between themselves.
No problem at this level.

Now, if I understand well, each router is also an Access point that can provide a connection to an external client.
So, I connect myself as a client using my laptop.
And here comes the strange thing.

The laptop can see only ONE Access point : the one that gave the connection.
But it cannot see the other Acces points of the WDS.
When I say “see” I am talking about pinging.
I have added another computer as a client.
And, actually, the laptop is capable of seeing it also.

This seems quite strange to me.

Also, all the MAC addresses are present in the client’s arp list (arp -a).

Is this a problem of routing ?
Do, I have to introduce routing tables somewhere ?


Another question.

The mesh documentation recommends to use two radio cards :
one for the WDS and the other for the AP.
It calls this, a dual radio card mesh.
The reason of this is to diminish interference.

The documentation also says that it is possible to use the same radio card for both tasks.
This is a single radio mesh network.
This is the approach I am following.

Please, can anybody give me an idea of what is happening ?

Thanks for your help.

Best regards,
Javier Revilla
ETH - Zurich

2

The laptop can see only ONE Access point : the one that gave the connection.
But it cannot see the other Acces points of the WDS.

what 802.11 mode that your laptop support it ?
what 802.11 mode that your access point support it ? ( antenna mode )

3

All radio cards are configured to the same band (2.4 GHz) and channel.
So 802.11-b/g

4

can the radio ping each other? if no, then you are having configuration problem.

5

As I have already said, all the Access points in the Wireless Distribution System can ping each other.
So, there is total connectivity between the APs.
When you add a client to any of the APs, then it can ping the AP that gave the connection.
But it cannot ping the other APs.
However, it can ping any of the clients that have connected to the same AP.

This is not how a WDS should work.
Imagine you want to monitor any of the APs from the client.
Well, right now you cannot.

Is this a problem of :

  • Configuration
  • Routing tables
  • A bug in Mikrotik’s software

This is an important issue and should be solved.
In my workplace, I recommended Mikrotik for the implementation of a mesh network.
So, I am expecting this solution to work.

Thanks,
Javier

6

There is a bug with HWMP+ where clients connected via WiFi have their MAC address added to the Mesh FDB as being LOCAL, but this FDB never expires, and is not removed when they disconnect. This can lead to the mesh not knowing where to forward packets for that client MAC, and is especially noticeable when you have WiFi clients that roam to another AP in the mesh.

This sounds like it may be the same issue ?

7

Another question,

Mesh radio A, B, C can ping each other?

Laptop connects to Mesh radio A, at which point your laptop is unable to ping Mesh radio B + C. (correct?)

With the laptop still connected to radio A, can mesh radio B ping mesh radio A? and A-B? B-C?

What exactly is dropping out when you connect?

JJOliver998.

8

Any more info on this issue, affected firmware versions etc, as Ive just deployed a 2 radio mesh with roaming across APS and didn’t realise this was a problem.

9

The issue only seems to appear when your client radio is bridged to a vlan on the mesh interface. We didnt see it until we had more than 3 AP’s and worked around it with EoIP tunnels, its a busy time of year for us so when things quiet down we will work with MT support to pinpoint it.

10

We have seen it on 5.4, 5.5 and 5.6 as thats all we tried.

11

Hello,

nz_monkey, JJOliver998 and riche_dav

Thank you very much for your answers.
Your comments are very interesting.
I will try to answer all your questions with only one reply.



1). Is this a bug ?

There is a bug with HWMP+ (...)
We have seen it on 5.4, 5.5 and 5.6 as thats all we tried.
I am using RouterOs v5.5.
And maybe it is a bug, indeed.
Several months ago, I made an experiment with a previous version of RouterOs.
And I did not have this problem.
If it is a bug, we should ask Mikrotik to intervene.
So, which would be the best way to ask Mikrotik to solve the bug ?



2). FDB table registration

There is a bug with HWMP+ where clients connected via WiFi have their MAC
address added to the Mesh FDB as being LOCAL, but this FDB never expires,
and is not removed when they disconnect. This can lead to the mesh not knowing
where to forward packets for that client MAC, and is especially noticeable
when you have WiFi clients that roam to another AP in the mesh.

Here you have the contents of the FDB tables (/interface mesh fdb print).
You can see that both clients are registered as "direct" in AP1.
However, in AP2, only cli_1 is registered, as "mesh".


AP1

Flag__MESH___TYPE____MAC-ADDRESS______INTERFACE___COMMENT
A_____mesh1___local_____00:0C:42:65:BA:C5_________________AP1
A_____mesh1___neighbor_00:0C:42:65:BB:25___11.8__________AP2
A_____mesh1___direct____00:1F:1F:7A:4A:C3___wlan1_________client2
A ____mesh1___direct____00:22:FA:51:7D:18____wlan1_________client1

AP2

Flag----MESH----TYPE------MAC-ADDRESS-------------INTERFACE-----COMMENT
A---------mesh1---neighbor-00:0C:42:65:BA:C5--------11.1------------------AP1
A---------mesh1---local--------00:0C:42:65:BB:25---------------------------------AP2
A---------mesh1---mesh ------00:22:FA:51:7D:18---------11.1------------------client1



3). Bridging to a vlan ?

The issue only seems to appear when your client radio is bridged to a vlan
on the mesh interface. We didnt see it until we had more than 3 AP's and
worked around it with EoIP tunnels, its a busy time of year for us so when
things quiet down we will work with MT support to pinpoint it.
I am not bridging to a vlan.



4). Detailed graphic description of the problem

What exactly is dropping out when you connect?

What I am trying to say is that a client can only ping the AP that give it a connection.
But cannot ping the other APs in the mesh.

Let's explain this with a simple case (two APs and two clients).
There are three possible cases :
(if you prefer a nice figure take a look at the attached PDF file)


a). First case - Two access points, no clients

AP1-----------AP2

I have a mesh network composed of two Mikrotik routers, with radio cards configured to the 2.4 GHz band (2467 MHz).
Both APs are capable of pinging each other.
AP1 pings AP2 : OK
AP2 pings AP1 : OK


b). Second case : Two access points, two clients

cli_1 ---> AP1-----------AP2
-----------------|
--------------cli_2

I add two clients that have radio cards with the same Wifi configuration than the APs (2467 MHz).
They both receive connections from AP1.
Still, both APs are capable of pinging each other.
Both clients are capable of pinging each other.
Both clients are capable of pinging AP1.
But none of the clients is capable of pinging AP2.

AP1 pings AP2 : OK
AP2 pings AP1 : OK
cli_1 pings cli_2 : OK
cli_2 pings cli_1 : OK
cli_1 pings AP1 : OK
cli_2 pings AP1 : OK
cli_1 pings AP2 : not possible
cli_2 pings AP2 : not possible


c). Third case : One client roams, drops his connection from AP1, and gets one from AP2

cli_1 ---> AP1-----------AP2 <---cli_2

AP1 pings AP2 : OK
AP2 pings AP1 : OK
cli_1 pings cli_2 : OK
cli_2 pings cli_1 : OK
cli_1 pings AP1 : OK
cli_2 pings AP1 : not possible
cli_1 pings AP2 : not possible
cli_2 pings AP2 : OK


So, as I said before, a client can only ping the AP that give it a connection.
But cannot ping the other APs in the mesh.
So, the mesh is not working as it should.

Thanks a lot for your help.

Best regards,
Javier
Zurich
mesh_mik.pdf (13.1 KB)

12

Here you have the three possible cases :
mesh_mik.pdf (13.1 KB)

13

(The bug…)

Have you tried the last version ?
RouterOs-5.7

By the way, I am using a RB433UAH, with v-5.5

Javier