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Ethernet Switches & Routers

Frequent Contributor
Posts: 117
Registered: ‎07-26-2010

MCT best practise regarding Spanning Tree

Hello all.

NetIron MLX MCT is of course avoiding STP to the switches connected via MC-LAG.

But STP is still a recommended point to be run at least on the MCT edge switches to detect and block loops.

But.... what is the best practise and your experience with STP configuration in the MCT setup at all?

- Are you running (R)STP on the MCT MLX switches? Single or per-VLAN?

- Is the MCT MLX (R)STP interworking with the (R)STP on the switches connected via MC-LAG?

- Or are you avoiding any interworking of (R)STP between any switches in this setup and prevent forwarding of L2 packets with "no


I have not found and recommendation or best practise on this from Brocade. Did anyone?

I know what the recommendation is on a similar setup with Cisco (VSS or vPC), since there are best practise papers available.

Thank you for any feedback.



Not applicable
Posts: 1
Registered: ‎01-28-2011

Re: MCT best practise regarding Spanning Tree

I know this post is a little old now - but it is good (sorry) to find someone else with the same issue. Did you get any response to this.

Initially I was looking at an MSTP configuration until it was pointed out that MSTP is not suppored over CCEP connections, therefore because the rest of my network would normally be configured with MSTP I am looking at RSTP single so that the MLX units I have will interoperate with any MSTP switches in their instance 0.

Whilst from what I have found it works there are a few issues that I have uncovered and am trying to get someone in Brocade to be interested in.

  • Root Protect seems to operate on one of the MCT nodes but the port state does not get copied over to the other MCT node.
  • When setting up RSTP in the first place it appears that the sequence used is important. Sometimes I have set it up and found that whilst a "show rstp" shows forwarding and fwd-by-mct that a display of the Vlans associated with the RSTP instance can show them as BLOCKING and traffic is not forwarded resulting in traffic loss.
  • I have also noticed that if you change the priority of a switch so that it is no longer root bridge - that the MCT peer (if it were meant to take over root bridge role) does not take over a root bridge.

From what I have seen so far however once it is set up and running it seems to work correctly.

Basic config I have applied is ...

rstp single

rtsp single priority xxxx (8192 or 16384 for primary and secondary devices)

rstp single ethernet xxx admin-pt2pt-mac

rstp single ethernet xxx admin-edge

vlan nnn


But I am unsure as to what the actual best practices are (like yourself)... should you for example disable RSTP on the Keepalive Vlan interface for example or even disable it on the ICL!!

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