[c-nsp] FW: Spanning-tree stupidity - MST not obeying cost /

[Collins, Richard (EXT)]

Just some ideas.....

 So with MST you should be using the command "spanning-tree mst 0 cost "
on the different trunk uplinks to skew the path.

SW3

interface FastEthernet0/1
 description Conn to SW4
 switchport
 switchport trunk encapsulation dot1q
  ......
 spanning-tree mst 0 cost 1000

Then you should be checking total path cost (cost of root path,
designated path cost)

Show spanning-tree mst detail....

Rgds,
Rich



>Message: 3
>Date: Sun, 20 May 2007 20:18:36 +0100
>From: Rolf Mendelsohn <rolf-web at cyberops.biz>
>Subject: [c-nsp] Spanning-tree stupidity - MST not obeying cost /
>       priority?
>To: cisco-nsp at puck.nether.net
>Message-ID: <200705202018.36921.rolf-web at cyberops.biz>
>Content-Type: text/plain;  charset="iso-8859-1"
>
>Hi Guys,
>
>I have the follow topology:
>
>
>               SW1
(Root)------------------------SW3------------------SW5
>               |     |                                              |
>               |     |                                              |
>               SW1------------------|               |
>                     -------------------SW4------------
>
>The topology is messy because of the fact that the switches are all
over town 
>running with different wireless links due to Radio/Geographical issues.
>
>I have MST instance 0 serving vlan's 1-1005.
>
>spanning-tree extend system-id
>spanning-tree mst configuration
>spanning-tree mst hello-time 1
>spanning-tree mst forward-time 6
>spanning-tree mst max-age 8
>spanning-tree mst max-hops 8
>
>SW1/SW2 = 3550
>SW3         = WS-3560
>SW4/SW5 = C2400ME
>
>SW1 bridge id 4096
>SW2 bridge id 8192
>SW4 bridge id 16384
>
>NO matter how high i set the cost and port-priority settings on the
link from 
>SW1 --- SW3, I cannot force the traffic to go via SW4----> SW1 (which
is the 
>way I would like it to go by default).
>
>Any idea's / hints would be much appreciated.
>
>