Another spanning-tree question

Question

Current network topology is something like this: I've recently added the M8024 switches to the network. They only have single uplinks to the 8024Fs, but when I rebooted them they seemed to bring down the connections to the equallogics. The  logs on the 8024Fs indicate a lot of this: 1/0/6 is transitioned from the forwarding state to the blocking state in instance 0Unit 1 elected as the new STP rootInstance 0 has elected a new STP root: a000:a4ba:db80:1e99Link down: 1/0/6Link on 1/0/6 is failedInstance 0 has elected a new STP root: 8000:d067:e57d:a0ecInstance 0 has elected a new STP root: 8000:d067:e57d:9ff01/0/6 is transitioned from the Forwarding state to the Blocking state in instance 0 The M8024's are generally at their default config in normal mode. An excerpt of the config of the interfaces connecting to the 8024F is .......... spanning-tree disablenospanning-tree port-priorityno spanning-tree portfastno spanning-tree tcnguardspanning-tree auto-portfastno spanning-tree guard rootno spanning-tree guard loop ............ The 8024F's have priority 40960 and the M8024s have 32768 so I understand the new switches being the new root bridge upon startup but why are there constant interfaces being blocked and new root bridge's being elected if there are no apparent loops?

Daniel My · Answer

Hello fs731

I would recommend that you make sure the interfaces to the EQL are in access mode. I checked with our EQL installer group to make sure access mode would not cause issues with the EQL connection. Our installer group informed me that is how they set them up, so it should cause no problems. They also advised to make sure the EQL is on its own VLAN. They also mentioned that the latest firmware has a lot of improvements for EQL. If you upgrade to a +4.0 firmware it will create a stack between the two 8024F's instead of a LAG, so be prepared for downtime related to any configuration issues if you upgrade.

Interfaces connected to servers/computers should be set to access mode. If they are not in access mode and take part in STP/RSTP elections then they have a chance of getting disabled.

If you are in the process of configuring M80s then you may want to set the priority on one of the 24F's to 4096 to make sure one of them is the root. This will cause less interruption from restarts on the M80's.

If that does not resolve the issue let me know.

Thanks

Daniel My · Answer

There may not be loops as we see them, but if endpoint interfaces are not in access mode and take part in the STP election process it is similar to creating loops. If putting them in access mode does not resolve the issue then please provide a more detailed layout of the cabling, interface numbers, and mac addresses of each unit.

Yes, portfast is recommended. It allows ports to switch modes faster. If a port is not in portfast then a computer may boot up faster than it can go into a forwarding state. If that happens and network authentication is required for login then the user will likely contact IT for a network issue.

fs731 · Answer

Thanks for the help.

I was more concerned with why ports were being blocked and flapping if there didn’t seem to be any loops in the M8024s. There are more switches attached to the 8024F’s also running STP which could of caused this?

Also in the documentation it seems Dell recommend using portfast on all edge ports (except for LAG interconnects I assume?) is this still the case?

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