Problem with Loop

[teppichmaler]

Hi Forum

I am new to alcatel.
In my Network i have OS6850 and OS6450 Switches.
actual Setup is:

Code: Select all

 SW1                         SW2
 6400-----------------------6850
|  | |------------------------|
|  |                                
|  --------
|         |
SW3       |
6850      |
|         |
|         |
|         |
SW4       |
6850------|

On All Switches are the same 20Vlans active.
On All Switches is Spaningtree in mode rstp active.

Now i will connect the SW2 with SW4 through a fibre.
But when i connect the fibre my network is going down.
On the Ports are the same Vlans tagged / untagged.

Can enyone give me a idea where my config mistake is?
thanks

[devnull]

If all switch are in the same stp mode (1x1) and have the same native/default vlan it should not go done.
can you share config / have a look at
show spantree
show spantree mode

Only other idea i'd have is there are some stp disabled devices/ports somewhere.

[teppichmaler]

Sorry for my late reply.
I think i found the problem.
On SW1 and SW2 ERP (Ethernet Ring Protection) are enabled.

to simplify the small network scheme in my first post, I have a few details underlined.
betwene the SW1 and the SW2 are about 15 other 6400 Switches. All are in one line betwene the SW1 and the SW2. On all these switches ERP is enabled.

I think the best way to get a stable network is to disable ERP on SW1 and SW2 and all the other switches. and get rstp running on all switches.
Or ist there a better solution?

[devnull]

I think using ERP means you use a Ring Topology.
With the introduction of a cable between SW2 and SW4 you will mess with your topology and create a loop. You can switch to RSTP (Remember maximum Hop count needs to be less than 40 in any case), but ERP has as far as i know way better convergence times (ERP >50ms, RSTP depending on topology and failure up to several seconds), so choose your poison.