Designated Port Election
Designated ports are ports that lead away from the root. Obviously, all ports
on the root bridge are designated ports (A-B and A-C in Figure 3-2).
■ Segment B-D—B has the lowest path cost to root (19 vs 119), so it is
designated for this segment.
■ Segment C-D—C has the lowest path cost to the root (100 vs 119), so
it is designated for this segment.
■ Segment B-C—B has the lowest path cost to the root (19 vs 100), so it
is designated for this segment.
■ Both segments D-E—D has the lowest cost to the root (57 vs 76), so it
is designated for both segments.
Now the looped topology has been turned into a tree with A at the root.
Notice that there are no more redundant links.