Wired Intelligent Edge (Campus Switching and Routing)


MAS Spanning tree options

i see this options

(spanning-tree) #mode ?
mstp                    Multiple spanning tree mode
pvst                    Per-Vlan rapid spanning tree mode



I was configuring agains an alcatel switch and o notice that i had spanning tree issues....

on my alcatel switch it uses rapid spanning tree but the default on the aruba switch is mstp which didnt work well... i had to change it to pvst and worked good


Now my question is which mode ihave to configure ?

I mean let say i need to use the mas agains a dell switch which use rapid spaning tree IEEE 802.1w sshould i use also pvst????


Anyone  :)




Product Manager - Aruba Networks
Alternetworks Corp
Super Contributor I

Re: MAS Spanning tree options


It depends on whether the attached network is sending you BPDUs on every VLAN, MST BPDUs on the native vlan, or just single BPDUs on the native VLAN.


In the last case you should be able to use either but with different vendors YMMV.  If you use MSTP on the MAS it won't mix well with PVST networks and I've seen some strange behaviors.  In the first case, use PVST.


If the network you are attaching to is running MSTP and you want the switch to participate fully in the network, you would have to set up MSTP on the MAS with the same MSTP configuration as the rest of the network and verify that the signatures on the configurations match (or equivalently that the link is marked as a "point-to-point" link not a "point-to-point boundary".)  If you do not, the switch will operate as though the entire network is one bridge, which will work for basic stuff but nothing advanced.


The commands may differ between vendors, but the MSTP configuration block itself is standardized so this works between vendors.


Contributor II

Re: MAS Spanning tree options

If a Mobility Access Switch running MSTP, receives RSTP/STP control packets from a neighbor, the neighbor is considered  "logically" to be in a different MSTP region.

 And for the RSTP/STP neighbor, the entire MSTP region looks like a single bridge.

All standard imlementations are usually designed to be backward compatible with the older versions, Plus "inter-op" with other vendors.


But, not to complicate things : If all these different devices are under your adminstrative domain, then it is better to run the same/consistent protocol across devices to avoid any inter-op issues, plus enabling ease of operation & debug.

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