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Spanning Tree

Posted on 2014-04-02
Medium Priority
Last Modified: 2014-07-14
I set my Vlans Spanning tree priority manually on my Core switch for Vlan 9, and my  Distro switch is using a 100M port that uplinks some access layer switches as the root port and its 1G uplink to the Core as a Desg forwarding port.  The Cost is higher on the 100M port.  Everything seems to work just fine but I'm a little puzzled and wondering if I'm missing something?  Why is the switch at the distro layer saying the 100M port to the access layer is the root?  Or is that the root for the Access layer switches and I am looking at it backwards?  

The ports in question on the Distro switch:
rotary@s07> show spanning-tree interface ge-0/0/47

Spanning tree interface parameters for instance 0

Interface    Port ID    Designated      Designated         Port    State  Role
                         port ID        bridge ID          Cost
ge-0/0/47.0    128:560       128:16  32768.00001da86531    200000  FWD    ROOT  100Mbps port speed link from Access Layer Switches


rotary@s07> show spanning-tree interface ge-0/1/0    

Spanning tree interface parameters for instance 0

Interface    Port ID    Designated      Designated         Port    State  Role
                         port ID        bridge ID          Cost
ge-0/1/0.0     128:609      128:609  32768.5c5eab668801     20000  FWD    DESG  1Gbps port speed uplink to Core Switch

Question by:rotarypwr

Assisted Solution

by:Hassan Besher
Hassan Besher earned 750 total points
ID: 39974043
well it's hard to tell until i see the full picture here, but if you want the core to be the root bridge for vlan 9 you simply type:

spann vlan 9 root primary

if i remember the correct syntax :)

the root port is the least cost to the root bridge so if in distro sw you see root port towards access layer it must be the least cost to get to the root bridge for vlan 9, after all write the previous command i told you before and notice if there is any diffrernces !
HTH :)
LVL 50

Accepted Solution

Don Johnston earned 750 total points
ID: 39974962
Why is the switch at the distro layer saying the 100M port to the access layer is the root?

Probably because you're not looking at the spanning-tree information for VLAN 9. Post the output from a "show spanning-tree vlan 9"

And if you use the "code" feature when posting the columns will line up.

Expert Comment

by:anila kiran
ID: 40194052
Capture.PNGplz upload any code related it ,,, how we show xml data in this tree

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