Configuration Guide User guide

1116 FastIron Configuration Guide
53-1002494-02
STP feature configuration
• Proposing – The Designated port on the root bridge sends an RST BPDU packet to its peer port
that contains a proposal flag. The proposal flag is a signal that indicates that the Designated
port is ready to put itself in a forwarding state (Figure 129). The Designated port continues to
send this flag in its RST BPDU until it is placed in a forwarding state (Figure 132) or is forced to
operate in 802.1D mode. (Refer to “Compatibility of 802.1W with 802.1D” on page 1136).
• Proposed – When a port receives an RST BPDU with a proposal flag from the Designated port
on its point-to-point link, it asserts the Proposed signal and one of the following occurs
(Figure 129):
• If the RST BPDU that the port receives is superior to what it can transmit, the port
assumes the role of a Root port. (Refer to the section on “Bridges and bridge port roles” on
page 1109.)
• If the RST BPDU that the port receives is inferior to what it can transmit, then the port is
given the role of Designated port.
NOTE
Proposed will never be asserted if the port is connected on a shared media link.
In Figure 129, Port3/Switch 200 is elected as the Root port
FIGURE 129 Proposing and proposed stage
Switch 100
Root Bridge
Switch 200
Switch 300 Switch 400
Port2
Designated port
Proposing
Port1
Root port
Proposed
Port2
Port2
Port3
Port3
RST BPDU
sent with a
Proposal
flag