STP Configuration Question

[mis03]

Hi All,

I am new to Extreme switching and currently looking to replace existing ICX6450-48P Edge switches with the 5420 models and need to know best practice for configuring these Edge switches with STP before connecting them to the network with other ICX switches.  The distribution/core is a ICX7750 and is not running any STP.  The existing ICX Edges have STP but PVST+ and MSTP is not enabled.    What STP configuration should be set for 5420 switches as these will be on boarded via Cloud XIQ and the requires the following STP settings to be configured for base template below.   Do I leave these with default settings ?   Is it likely to caused any issues if switch is connected to dist/core or daisy-changed to another ICX Edge Switch ? What is the best approach ?

Extreme Cloud XIQ template STP settings-

STP MODE
1) STP
Initial version of this protocol uses a single tree without regard to VLAN. After convergence (30-50 seconds), only the root bridge sends configuration BPDUs (Bridge Protocol Data Units).

2) RSTP (Rapid STP)
Like STP, RSTP uses single tree without regard to VLAN. After convergence (a few millisecond - 6 seconds), all switches send BPDUs every 2 seconds.

3) MSTP (Multiple STP)
MSTP (Multiple Spanning Tree Protocol) can map a group of VLANs into a single Multiple Spanning Tree instance (MSTI).

STP BRIDGE PRIORITY = 32768 (Default)

STP TIMERS
Forward Delay = 15 (Default)
This is the time the switch spends in the listening and learning state. The default is 15 seconds, the range is 4 to 30 seconds.

Max Age = 20 (Default)
This is the maximum time period before a bridge port saves its configuration BPDU information. The default is 20 seconds, the range is 6 and 40 seconds.

[Nicolas_Melay]

MSTP is the current standard STP protocol, and frankly the only one that should be used, on any brand (and drop those that don't support it).
That being said, running MSTP with only the default CIST instance is roughly equivalent to RSTP.
Also, RSTP is not supposed to be any faster than MSTP, it's only faster than the original STP (that should not be used anymore, anywhere).
So go for RSTP or MSTP, it does not really matter.

*** Thereafter, STP means MSTP or RSTP, NOT the original STP ***

As Gabriel briefly mentioned, there's a serious issue with EXOS STP support: each new VLAN needs to be manually added to an existing STP instance, only VLAN 1 defaults to being enabled for STP.
I'm not familiar with XIQ onboarding of EXOS switches -- only tried it when it was brand new and trashed your EXOS configuration.
Gabriel seems to say XIQ works around this STP-not-enabled-on-new-VLANs problem. Good to know!

On a NOT XIQ-managed EXOS switch, there are various strategies to alleviate this issue.
One is to create a dedicated VLAN, enable it for STP, add tag it on every port (or rather add every port tagged to this VLAN, in the EXOS way).
Another one is to run a script on your switch named ezspantree.py, which will monitor new VLAN creation, and add every new VLAN to the RSTP instance of the CIST MSTP instance. But the background process started by this script sometimes stops working (apparently when your switch has a long enough uptime), and makes VLAN creation a dangerous operation again.

So, running STP on EXOS is not without issue, hopefully XIQ does a good job at working around this, but anyway don't forget to test your setup and make sure your network is really loop-proof.

[Gabriel_G]

Hello!

Best practice is to have all switches running STP use the same version of STP with all of the same timers based on your network design. By default, EXOS/SwitchEngine switches are running MSTP with all ports in the default VLAN being automatically added into STP. To extend this default setup, simply add other ports/VLANs into STP, which is already the default setting in the XIQ default port types. You may need to change your cisco switches to MSTP considering that most of PVST+ is locked down by Cisco.

Hope that helps!

[mis03]

Hello Gabriel, Thank you for reply.

Sorry have existing Ruckus ICX switches running RSTP 802..1w running on the Core and Edges.   Is it better to keep running on RSTP or better to move to MSTP ?  RSTP has faster convergence.

In any case not sure how to migrate to MSTP with new EXOS Extreme edge switches that are going to be replaced.  Can this be a phased approach when adding new switches without disruption because the spanning tree reconfiguration can disrupt the traffic flow and if so how can I do this ?