Spanning Tree Port Priority

Spanning Tree Port Priority

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Subject Author Date
Spanning Tree Port Priority bpanders71 08-31-2005
Posted by on August 31, 2005, 11:05 am
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In my configuration report of my HP 4000m Procurve switch there lists a
section for Spanning Tree Operation, then a listing of ports and a
priority number. I just barely understand this end of IT, but realize
a lower number represents higher priority. However, if my config
report states Spanning tree is not enabled, do these priority numbers
matter? All but one are set at 128, and one is at 64. (Follow up
questions to come if this matters despite STP being disabled)

Any good online referrences to explain this stuff to me better? The HP
management and config guide doesn't help me much.

Thanks-
Brian



Pure Networks
Posted by Albert Manfredi on August 31, 2005, 12:53 pm
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bpanders71@hotmail.com wrote:
> In my configuration report of my HP 4000m Procurve switch there lists a
> section for Spanning Tree Operation, then a listing of ports and a
> priority number. I just barely understand this end of IT, but realize
> a lower number represents higher priority. However, if my config
> report states Spanning tree is not enabled, do these priority numbers
> matter? All but one are set at 128, and one is at 64. (Follow up
> questions to come if this matters despite STP being disabled)
>
> Any good online referrences to explain this stuff to me better? The HP
> management and config guide doesn't help me much.

You can go to the IEEE web site and download 802.1D. Find the getieee
button to do this.

In IEEE 802.1D, Clause 17 discusses the Rapid Spanning Tree Protocol,
and refers back to Clause 9 for a discussion of the priority bits.
These priority bits are part of the overall Switch ID (64 bits) and
Port ID (16 bits). By configuring the priority bits, a network
administrator can encourage the RSTP to use certain switches and data
paths preferentially.

However, I don't know where HP finds enough bits for 128 levels. The
IEEE standard mentions 3 or 4 bits assigned specifically to priority,
not 7 bits.

Anyway, I would think that if RSTP is disabled, then how these bits are
set should not matter.

Bert



Posted by on August 31, 2005, 3:55 pm
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Thanks guys, that's kind of what I thought, but being a newb to this
end of the spectrum, had to ask.

Thanks!
Brian



Posted by Rich Seifert on August 31, 2005, 12:55 pm
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bpanders71@hotmail.com wrote:

> In my configuration report of my HP 4000m Procurve switch there lists a
> section for Spanning Tree Operation, then a listing of ports and a
> priority number. I just barely understand this end of IT, but realize
> a lower number represents higher priority. However, if my config
> report states Spanning tree is not enabled, do these priority numbers
> matter? All but one are set at 128, and one is at 64. (Follow up
> questions to come if this matters despite STP being disabled)
>
> Any good online referrences to explain this stuff to me better? The HP
> management and config guide doesn't help me much.
>

Spanning Tree port priorities don't have any effect if the Spanning Tree
Protocol entity itself is disabled.


--
Rich Seifert Networks and Communications Consulting
21885 Bear Creek Way
(408) 395-5700 Los Gatos, CA 95033
(408) 228-0803 FAX

Send replies to: usenet at richseifert dot com


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