Edge Port - Huawei AR530 series Configuration Manual

Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
Figure 6-12 Proposal/Agreement negotiation process
(Leaves the port
state unchanged)
The Proposal/Agreement mechanism works as follows:
1.
2.
3.
4.
5.
6.
7.
The proposal/agreement process can proceed to downstream devices.
STP can select designated ports quickly; however, to prevent loops, all ports must wait at least
one Forward Delay interval before starting data forwarding. RSTP blocks non-root ports to
prevent loops and uses the proposal/agreement mechanism to shorten the time that an upstream
port waits before transitioning to the Forwarding state.
Issue 01 (2014-11-30)
S1
p0
3 Agreement
p1
S2
p2
p3
2 sync 2 sync
(Blocks the
port)
p0 and p1 become designated ports and send RST BPDUs to each other.
The RST BPDU sent from p0 is superior to that of p1, so p1 becomes a root port and stops
sending RST BPDUs.
p0 enters the Discarding state and sets the Proposal field in its RST BPDU to 1.
After S2 receives an RST BPDU with the Proposal field set to 1, it sets the sync variable
to 1 for all its ports.
As p2 has been blocked, its state remains unchanged. p4 is an edge port and does not
participate in calculation. Therefore, only the non-edge designated port p3 needs to be
blocked.
After p2, p3, and p4 enter the Discarding state, their synced variable is set to 1. The synced
variable of the root port p1 is also set to 1, and p1 sends an RST BPDU with the Agreement
field set to S1. This RST BPDU carries the same information as the one sent from the root
bridge S1, except that the Agreement field is set to 1 and the Proposal field is set to 0.
After S1 receives this RST BPDU, it identifies that the RST BPDU is sent in response to
the proposal that it has sent. Then p0 immediately enters the Forwarding state.
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1 Proposal
E
p4
2 sync
(leaves the port
state unchanged)
Designated port
Alternate port
E Edge port
6 STP/RSTP Configuration
186