Set low RSTP priority on external switch

[Antonio_73]

We have two 5304XL which act as root switches among our vlans (switches do not route), giving double connections to all our servers and smaller switches.
A customer asked to give him double connection to his rack's switch, so we are planning to connect his switch to both 5304XL.
We want to use RSTP, but we want the customer switch to have the lowest priority (or none), despite how he (mis)configures his switch.
Any hint on how to force that on our side?
Thanks,
Tonino

[Shadow13]

If you don't have access to the cu's switches then there is no way to do that, what you can do is to configure the 5304xl switches with the LOWEST priority (as the lowest priority will be the root), but you might face a problem if the cu's switches are also configured with same priorities (same as your switches) in this case the MAC address of the switches will be checked and the switch with the lowest MAC address will be come the root.

So if you don;t have access to these switches it will depend on your luck :) whether the cu's switches will have the lower MAC or your switches (the 5304zl)

[Antonio_73]

There is also no way to have no RSTP at all with them?
Just forcing our ports as directed to simple server, disabling any RSTP protocol?

[Pieter 't Hart · Accepted solution]

Look at the "Command Line Interface Reference Guide", some otions are
-
â   root-guard -- Set port to ignore superior BPDUs to prevent it from becoming Root Port.(p. 565)
â   bpdu-filter -- Stop a specific port or ports from transmitting BPDUs, receiving BPDUs, and
assume a continuous fowarding state.(p. 554)

you may also consider making the connection using a (redundant) routed link instead of using spanning-tree?

[Antonio_73]

It looks like root-guard is the solution we need.
Dual routed link is too complex, because would force customer to add a routing device, instead of a simple switch.
Thanks,
Tonino