Dell Brocade DCX, Configuration Manual

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330 BigIron RX Series Configuration Guide
53-1001810-01
IEEE Single Spanning Tree (SSTP)
12
IEEE Single Spanning Tree (SSTP)
By default, each port-based VLAN on the device runs a separate spanning tree, which you can
enable or disable on an individual VLAN basis.
Alternatively, you can configure the device to run a single spanning tree across all of its ports and
VLANs. The SSTP feature is especially useful for connecting a device to third-party devices that run
a single spanning tree in accordance with the 802.1q specification.
SSTP uses the same parameters, with the same value ranges and defaults, as the default STP
supported on the device. Refer to
“Default STP bridge and port parameters” on page 321.
SSTP defaults
SSTP is disabled by default. When you enable the feature, all VLANs on which STP is enabled
become members of a single spanning tree. All VLANs on which STP is disabled are excluded from
the single spanning tree:
•
To add a VLAN to the single spanning tree, enable STP on that VLAN.
STP port parameters
Port number and STP state The internal port number and the port’s STP state.
The internal port number is one of the following:
•
The port’s interface number, if the port is the designated port for
the LAN.
•
The interface number of the designated port from the received
BPDU, if the interface is not the designated port for the LAN.
The state can be one of the following:
•
BLOCKING – STP has blocked Layer 2 traffic on this port to prevent
a loop. The device or VLAN can reach the root bridge using another
port, whose state is FORWARDING. When a port is in this state, the
port does not transmit or receive user frames, but the port does
continue to receive STP BPDUs.
•
DISABLED – The port is not participating in STP. This can occur
when the port is disconnected or STP is administratively disabled
on the port.
•
FORWARDING – STP is allowing the port to send and receive
frames.
•
LISTENING – STP is responding to a topology change and this port
is listening for a BPDU from neighboring bridges in order to
determine the new topology. No user frames are transmitted or
received during this state.
•
LEARNING – The port has passed through the LISTENING state and
will change to the BLOCKING or FORWARDING state, depending on
the results of STP’s reconvergence. The port does not transmit or
receive user frames during this state. However, the device can
learn the MAC addresses of frames that the port receives during
this state and make corresponding entries in the MAC table.
NOTE: If the state is DISABLED, no further STP information is displayed
for the port.
TABLE 73 CLI display of detailed STP information for ports (Continued)
This field... Displays...