Vlan with multi root...!!!

[marokim.mit]

hi every body ...i am new in your community...my name is abdelhakim...and i have a probelm in my project...
i have question can we have a vlan with more root stp...because i found the same...and more then that i found some vlan with multi root who share the same priority...and other Vlan also multi root and not the same priority...is't a problem or what??...and thanks

[Antonio Knox · Accepted solution]

Make sure that your switches are running the same spanning tree protocol (ie PVST+, RSTP, etc).  Secondly, make sure you don't have any VTP transparent switches out there.  They will break up your spanning tree since they don't respond to BPDUs.  This means that if you have:

Switch 1 <--------> Switch 2 <--------> Switch 3

Let's say Switch 1 is supposed to be root bridge.  If Switch 2 is transparent, then he won't respond to or forward BPDUs he receives, so Switch 1 will think that he is (and rightfully so) the root bridge since he's seen no superior BPDUs.  At the same time, Switch 3 doesn't see superior BPDUs since Switch 2 isn't sending any, so he thinks he is root as well.  You see, it's easier than you may think to have 2 root bridges.  Just make sure everything is set up as it should be.

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[marokim.mit]

thanks Mr antonio. my archictcure like this

Switch1------------------------Switch2
    |                                   |

    |                                   |
Switch3------------------------Switch4

    |                                   |

    |                                   |
Switch5------------------------Switch6

Switch1 and Switch2 are in mode transparent ,and Switch3 and Switch4 are in mode server and Switch5 and Switch6 are in mode Client,the racine in my network are Switch1 and Switch4(small priority) with different prioritys...for Switch2 considered Switch 1 as root and all others considered Switch4 as root...finaly i found that u have a reason...thanks you again...and if u have  a document to explain that more i will be apreciate...