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RE: spanning-tree and port priority posted 08/02/2003
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http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114ea1/3550s
cg/swstp.htm#1020470

quote:
IF A LOOP OCCURS, spanning tree uses the port priority when selecting an
interface to put into the forwarding state. You can assign higher
priority values (lower numerical values) to interfaces that you want
selected first and lower priority values (higher numerical values) that
you want selected last. If all interfaces have the same priority value,
spanning tree puts the interface with the lowest interface number in the
forwarding state and blocks the other interfaces. 
end quote

Note my emphasis on the phrase "if a loop occurs". My interpretation of
the paragraph above is that the switch IOS ignores port priority until a
loop occurs.

HTH


-----Original Message-----
From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf Of
John Matijevic
Sent: Saturday, August 02, 2003 12:14 PM
To: John Matijevic; ccielab@xxxxxxxxxxxxxx
Subject: Re: spanning-tree and port priority


Team,
If anyone can get this to work using port-priority command please let me
know. Otherwise I am assuming the DocCd is wrong that the port-priority
value modification does not make a difference.
The only way I could change the state from forwarding to blocking was to
adjust the cost. In my initial thinking based on the DocCd I thought I
could
do this with the port-priority. I even tried using the value 112. Based
on
the following:
Valid priority values are 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160,
176, 192, 208, 224, and 240. All other values are rejected.

Sincerely,

Matijevic

----- Original Message ----- 
From: "John Matijevic" <matijevi@xxxxxxxxxxxxx>
To: <ccielab@xxxxxxxxxxxxxx>
Sent: Saturday, August 02, 2003 11:29 AM
Subject: spanning-tree and port priority


> Hello Team,
> I know there is an ealier thread on 7/7/03, on this that I read, but
no
> response.
> I am trying to change the state from blocking to forwarding on a
non-root
> switch.
> I used the command under interface:
> spanning-tree vlan 1 port-priority 100,
> By lowering the priority the port should go into forwarding state and
the
rest
> should be blocking. However, this is not happening, I know there was
an
> earlier thread on this but there was no response.
> p1s2#sh span vlan 1
>
> VLAN0001
>   Spanning tree enabled protocol ieee
>   Root ID    Priority    24577
>              Address     000b.be5d.5b80
>              Cost        19
>              Port        21 (FastEthernet0/21)
>              Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
>
>   Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)
>              Address     000b.46d9.2580
>              Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
>              Aging Time 300
>
> Interface        Port ID                     Designated
Port
> ID
> Name             Prio.Nbr      Cost Sts      Cost Bridge ID
> Prio.Nbr
> ---------------- -------- --------- --- --------- --------------------
> --------
> Fa0/21           128.21          19 FWD         0 24577 000b.be5d.5b80
128.21
> Fa0/22           128.22          19 BLK         0 24577 000b.be5d.5b80
128.22
> Fa0/23           128.23          19 BLK         0 24577 000b.be5d.5b80
128.23
> Fa0/24           100.24          19 BLK         0 24577 000b.be5d.5b80
128.24
>
> p1s2#
> port fa0/21 is the port im trying to change, on the non-root switch.
> Any suggestions?
> Sincerely,
> Matijevic
>
>
>
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