Changing topology after connecting to OS 6250

[mohdkw]

Hi

I am using 9000 for my network , it is a star topology that distributes to many omnistack switches.

When one of the omnistack switch failed , i replaced it with OS 6250 . However, a strange thing happened to my network when i connected the OS 6250 ( default configuration) to the OS9000 through fiber. Once i connected the 6250 to 9000 , the whole network went down , the traffic stopped. when i checked the logs in OS9000 i found a msg saying "Topology changed" , when i disconnected OS 6250 from OS9000, the network came up and the traffic start passing.


Any ideas guys what cause this issue ?

[devnull]

Seems like STP.

So probably your new 6250 had a better priority than the 9000?
In that case a root bridge is changend resulting in all non-Edge Ports going to blocking. But it should (even while not wanted) resume working after ~1 Minute.

[mohdkw]

Thanks for replay

Where can I check the priority on both , should I make 9000 higher number or lower to make sure it will not be interrupted if I connected any switch ?

[devnull]

You core switch(s) should alway have the lowest priority in your network as low means = rootbridge.

Default is 32768, so anything better than that is fine. I would set it to 16384 or 8192 for compatibility and it leaves a possibility to "insert" something better

Depending on your STP mode (1x1 or MSTP/STP) you set it per vlan, per instance or globally.

[mohdkw]

Thanks , I will have a look

[mohdkw]

How can change the priority? Also what is the proper setup for stp mode?

[devnull]

I think this are some kind of network basics that you should have learned? I mean you use several 10k hardware..

You should use the same STP on your 6250 as you have configured on your 9X00.

If you use Alcatel 1x1 you shoud use 1x1 if you use MSTP you should not try something else i guess.

So what is currently in use?

Changing the prioity is different depending on mstp or 1x1 or Flat spanning tree.

Do
"show spantree" on your 9700 here you see your mode.
This should be reflected in your 6250 as well.
Depending on your setup (VRRP? Different prioritys for the vlans?) you should make one 9700 Root bridge or split the roots for different vlans (have vrrp master be rootbridge for the vlan as well.

e.g.
bridge 669 priority 8192
bridge 670 priority 8192
bridge 671 priority 8192
bridge 672 priority 16384
bridge 674 priority 16384

doing a
"show spantree 672"
(or spantree vlan 1) should everywhere in you lan (where the vlan is used) point to the same root bridge ID.