Redundant link between Mikrotik bridge devices - RSTP?

RouterOS General
1

Hello people!

I want to create a backup link between 3 Mikrotiks where I’ve all the interfaces in Bridge.

I’m thinking in use RSTP and than define different costs on the backup interfaces, but I can do it working well.

See my topology:

  • I’ve the interface ehter1 and ether2 of all routers in the Bridge1;
  • The IP address of the routers is configurated on the Bridge1;
  • I’ve the RSTP activated on all routers;
  • On routers 192.168.88.2 and 192.168.88.3 I configurated the PATH COST as 100 on ether2 (backup link) and keep PATH COST as 10 on ether1.

The problem is that the RouterOS sometimes use ether1 as root port and keep the ether2 as alternate port, sometimes put the ether2 as backup and sometimes use the ether4 as root port.

I need to have the control and just use the ether2 if the ether1 of router 192.168.88.2 and 192.168.88.3 is down.

Thanks!

2

Change bridge and port ‘priority’ parameter to force root bridge selection and force port to ‘designated’ role.
Lower number = higher priority.
For interfaces with the same speed same set same ‘path cost’ value.
Useful link:
http://en.wikipedia.org/wiki/Spanning_Tree_Protocol

HTH,

3

Thanks ditonet!

What do you say with “change bridge”? Thanks!

And I need to have the RSTP configurated on the 3 routers or justo on the routers with the backup link?

Thanks!

4

You could also use hwmp+ for this

5

What do you say with “change bridge”?

Change bridge ‘priority’ and port ‘priority’ parameters.
‘Priority’ makes possible to achieve fixed ‘startup’ configuration of your network (root bridge, designated ports, etc.)
Configure RSTP on every device.

HTH,

6

Thanks again ditonet, but sorry me!

Where can I configure the bridge priority? I just see the priority option on bridge->port.

Thanks!

7

Hi,

In Winbox you should go to Bridge

  1. Double click on your bridge interface (bridge1 if Im not mistaken)
  2. Click the STP tab
  3. You’ll find Prioty and change it as stated above

Root Bridge should have lowest priority..

Or change from terminal:

/interface bridge
add admin-mac=00:00:00:00:00:00 ageing-time=5m arp=enabled auto-mac=yes \
    comment="" disabled=no forward-delay=15s l2mtu=2290 max-message-age=20s \
    mtu=1500 name=hotspot priority=0x8000 protocol-mode=none \
    transmit-hold-count=6

Please post the reuslts if it worked…and if it is still switchingbeetwen ether ports…

Regards,
Huntah

8

Thanks for the reply!

But I just have 1 bridge on each router and all interfaces on this bridge! I need to change the bridge priority and put the some value on all routers or I need to put different value on each routers?

And another question, why the router 192.168.88.3 doens’t show the ether2 as Alternate port? It’s showing as designated port.

Thank you very much!

9

@conchalnet
Try Googling some info how exactly (R)STP works.
Do not set same bridge ‘priority’ on every device.
Bridge with lowest ‘priority’ becomes ‘root bridge’ during selection.
If all your bridges have same ‘priority’ rooot bridge selection is based on bridge MAC-address.
Port with lowest ‘priority’ becomes ‘designated port’, even if other ports have same path cost to root bridge.

HTH,

10

thanks ditonet, i ready someting about rstp last night! thank you very much!

I’ve just 3 doubts now:
1-in my scenary what is the root bridge in your opinion?
2-the another 2 routers can I use the same bridge priority?
3-what’s the difference between “Alternative port” and “Backup port” on the port role?

Thank you again!

11

Hello,

I have 2 offices with 20 machines in each office. We had diferent ip range in the 2 offices.. We had the ospf setup with 2 rb450 (one in each office) and 2 WDS links with 411AH.

Now the customer wants to use the same ip range in both offices. We reconfigured the network and we activated a bridge in the 2 interfaces where the antennas are connected in RB450’s.. We activated the RSTP and changed the path cost to 9 (main link) and 100 (backup link). The setup works well, except when the main link disconnects (we make a test disabling one radio).

The backup link doesn’t start working.. no traffic on it. You can contact with the computers in your side, but not in the other side. Why?¿?

It’s possible we have to use 8 path cost for main, 9 for backup and 10 (default) for other ports of the bridge¿?

thanks,