From: Bob Sinclair (bsin@cox.net)
Date: Wed May 26 2004 - 16:01:29 GMT-3
Sam,
Port ID is only relevant when you are dealing with parallel links between
switches. To determine the root port on a non-root bridge, the bridge first
compares root path cost on alternate paths. If they are equal, then the
bridge compares sender BIDs. If sender BIDs are equal, then it must be
parallel links to the same switch. In this case, port id becomes the final
tie-breaker.
If you have parallel links, you can determine the root port using path cost
or port id, though port ID would be preferred.
1. you can increase the port cost on the less-desired port, or decrease port
cost on the more preferred port. Remember root path cost is the sum of
cumulated cost plus ingress cost.
2. you can decrease the port priority on the port upstream of the port you
do not want to become the root port, or you can increase the port priority
upstream of the port you want to become the root port.
HTH,
Bob Sinclair
CCIE #10427, CISSP, MCSE
www.netmasterclass.net
----- Original Message -----
From: <samccie2004@yahoo.co.uk>
To: "studygroup" <ccielab@groupstudy.com>
Sent: Wednesday, May 26, 2004 1:47 PM
Subject: Port Priority" Vs "Path Cost
> Hi Group
>
> Though I read TAC, I am still unclear about what is different between the
2
> options.
> When do u prefer "Port Priority" Vs "Path Cost" and vice versa. They seem
to
> both achieve the same results.
>
> TIA
>
> Sam
>
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