From: Hogo, Trust (trust.hogo@sarcom.com)
Date: Sun Feb 29 2004 - 02:38:47 GMT-3
Please note that by default all ports on the root switch are
forwarding. For example all fast-Ethernet ports by default have
port-priority of 128 and a port cost of 19. So with everything else
being equal the tie breaker becomes the port-id, which means the lowest
port is selected to forward all traffic. Port 13 will be preferred than
port 14 with everything else being equal. Please note the port that will
be blocked id the downstream port not the port on the root switch. To
change this behavior on the root switch so as to prefer port 14 versus
13 use port-priority and the downstream port will now block 13 and
forward 14. Port-priority affect the directly connected switch. Port
cost affect the entire switch domain. A lower cost is preferred than a
higher cost. If you want to have the same effect as stated above without
changing the root switch or port-priority then you change the port of
cost of the downstream switch and make it lower than the default 19 and
you will be able to archive the same thing.
Hope is helps
Trust
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Hossam
Sent: Saturday, February 28, 2004 5:25 PM
To: ccielab@groupstudy.com
Subject: Root Port election process in SPT!
Group,
I understand that SPT while electing the root port for a switch goes in
the following sequence:
1- Port Cost
2- Port Priorty
3- Port ID
In my lab setup this goes only when the two candidate root ports are
connected to ONE switch
CATA CATB CATC--- ROOT
|--FA 0/1--FA 0/1---| |
| |-FA 0/3-----FA 0/3 ----|
|--FA 0/2--FA 0/2---| |
In the above diagram everything goes as expected. CATA-FA0/1 is FWD
while CATA-FA0/2 ius BLK.
When i change port-priorty on CAT B-FA0/2 to 64 the roles are reversed.
CATA-FA0/1 is BLK and CATA-FA0/2 is FWD. SO far so good.
My problem is when i replace CAT B with two separte Switches.
CATA CATB1 CATC--- ROOT
|--FA 0/1--FA 0/1---|--- FA0/3---FA0/3 ----|
| |
|
|
|
|
|
| |--- FA 0/3--FA 0/3 ----|
|--FA 0/2--FA 0/2---| |
CATB2
In this setup CATA-FA 0/1 stays FWD even when i change the CATB2- FA0/2
port Priorty to 64?
I can only change the ROot port via the Port cost command in the second
scenario?
For me it seems that port priorty does't envolve in the root port
election process if the two candidate ports are connected to the same
switch!!
Is that regular? or is there something that i am missing?
Thanks
SAM
---------------------------------
Do you Yahoo!?
Get better spam protection with Yahoo! Mail
This archive was generated by hypermail 2.1.4 : Fri Mar 05 2004 - 07:14:00 GMT-3