Ethernet Switches & Routers

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Occasional Contributor
Posts: 6
Registered: ‎06-09-2010

FCX 648 Spanning-tree issue.

I am in the process of deploying FCX 648 switches, and have recently encountered a spanning-tree reconvergence when I enable uplinks to MLX.  I have 'spanning-tree root-protect' on MLX side, but when uplinks are enabled I still have a reconvergence and recalc.

Has anyone else experienced this, and if so what solution was implemented.

Contributor
Posts: 50
Registered: ‎01-07-2011

Re: FCX 648 Spanning-tree issue.

This is from the MLX configuration guide:

NOTE
Root Guard may prevent network connectivity if improperly configured. It needs to be configured on
the perimeter of the network rather than the core. Also, Root Guard should be configured only on the
primary port of a LAG.

It sounds like you have Root Guard configured on your core switch (MLX).

Occasional Contributor
Posts: 6
Registered: ‎06-09-2010

Re: FCX 648 Spanning-tree issue.

Thanks for the response, we are 'only' using root protect on uplink ports connecting from MLX to FCX but still experience recalc and re-convergence upon turn up?

Super Contributor
Posts: 1,087
Registered: ‎12-13-2009

Re: FCX 648 Spanning-tree issue.

Hi,

     What spanning tree are you using (STP,RSTP, MSTP etc)?

     Note root guard will not do anything when MSTP is used.

     Which switch do you want as the root? Have you set that switch with a lower prioity?

Can you please provide a network layout?

Thanks

Michael.

Occasional Contributor
Posts: 6
Registered: ‎06-09-2010

Re: FCX 648 Spanning-tree issue.

Thank you very much for your assistance, After further investigation, I noticed that links to existing Cisco 6500's are becoming root when I turn up new FCX's connected to our MLX's via root protected ports.  For some reason turning up a new FCX causes a spanning tree recalc that leaves the Cisco as root bridge and puts network in chaotic state until FCX ports are disabled and MLX's reassume root.  Could this be a result of not using VLAN 1 on Brocades, which is Cisco default VLAN?

Super Contributor
Posts: 1,087
Registered: ‎12-13-2009

Re: FCX 648 Spanning-tree issue.

Hi,

     What type of STP are you using on the FCX and MLX and 6500's?

     Do you want the MLX to ALLWAYS be the prefered Root bridge?   If so they lower its prioty to a lower value then the 6500's.

   Thanks

Michael.

Occasional Contributor
Posts: 6
Registered: ‎06-09-2010

Re: FCX 648 Spanning-tree issue.

RSTP, MLX should always be root.  

Contributor
Posts: 50
Registered: ‎01-07-2011

Re: FCX 648 Spanning-tree issue.

Would you mind posting the spanning-tree config from the 6509, FCX and the MLX?

Occasional Contributor
Posts: 6
Registered: ‎06-09-2010

Re: FCX 648 Spanning-tree issue.

Unfortunately my name would dissapear from my paycheck if I post proprietary info of that nature, but I can say that the LAG's to Cisco's do not have root protect on primary lag member, could this be the reason that the Cisco's are becoming root.  Or could it be the path costs perhaps?

Super Contributor
Posts: 1,087
Registered: ‎12-13-2009

Re: FCX 648 Spanning-tree issue.

Configure on your MLX a priority value of 0 (this is the highest priority).  You need to do this for each VLAN that are running RSTP.

You can also use root guard on the LAG's to the CISCO however using the priority should  stop that that too.

To designate a priority for a bridge, enter a command such as the following at the VLAN level.

NetIron(config)# vlan 20

NetIron(config-vlan-20)# rstp priority 0

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