Disabling STP on IBM Bladecenter

[christophermcintosh]

The current networking I'm working with is currently using STP. I would like to upgrade to RSTP, all the devices support it except our IBM Bladecenter. The Bladecenter has a 4portGB Ethernet Switch Module(ESM). The four ports on the ESM are joined together using LACP to a switch. Since the ports are using LACP perventing loops can I disable STP on the IBM Bladecenter and upgrade the network to RSTP. I thought about it a bit because the importance of STP but I think this will work, but want to get some other opinions.

[smehrnia]

Hi Chris.

that would work, but what if LACP fails at some point, by disabling STP in any L2 network you have a risk of encountering a loop one day, or creating one by mistake.

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml#comp802

plz Rate if it helped.

Soroush

[Giuseppe Larosa · Accepted solution]

Hello Christopher,

RSTP can fall back to STP on a per port basis so you can enable RSTP in all of your network without disabling STP on the blade center.

There is a version field in the BDPU frame format so RSTP switch can easily detect the legacy device on the bundle.

This provides you more safety as you haven't disabled STP

Hope to help

Giuseppe

[christophermcintosh]

Giuseppe I didn't realize it would fall back on a per port basis. I guess my question would be sence one port fell back to STP won't that cause the convergence back to the speed of STP for the whole network? Would there be any advantage of going to RTSP?

[smehrnia · Accepted solution]

RSTP is able to interoperate with legacy STP protocols. However, it is important to note that the inherent fast convergence benefits of 802.1w (RSTP) are lost when it interacts with legacy bridges, but since it occures on a per port basis, it shouldnt be a problem for ur topology. 802.1D will only run between ur switch and ur IBM, the rest of the network will do RSTP.

also, RSTP natively includes most of the Cisco proprietary enhancements to the 802.1D spanning tree, such as BackboneFast, UplinkFast, and PortFast. RSTP can achieve much faster convergence in a properly configured network, sometimes in the order of a few hundred milliseconds. Classic 802.1D timers, such as forward delay and max_age, are only used as a backup.

note that, in an environment running Rapid STP the final topology is exactly the same as the one calculated by 802.1D (that is, one blocked port at the same place as before). Only the steps used to reach this topology have changed and it is much faster of course!

so depending on the size and topology of ur network, it is your choice to choose between upgrading and not upgrading to RSTP.

plz Rate if it helped.

Soroush

[christophermcintosh]

Thanks everyone for your input. I will probably go ahead with with RSTP and keep the one port using STP.

[glen.grant]

   Kind of surprised to hear it doesnt support rspt . What code version are the switches running ?