Brocade Communications Systems Brocate Ethernet Access Switch 6910 User Manual
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Brocade 6910 Ethernet Access Switch Configuration Guide
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Configuring Interface Settings for STA
36
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Root Guard – STA allows a bridge with a lower bridge identifier (or same identifier and lower
MAC address) to take over as the root bridge at any time. Root Guard can be used to ensure
that the root bridge is not formed at a suboptimal location. Root Guard should be enabled on
any designated port connected to low-speed bridges which could potentially overload a slower
link by taking over as the root port and forming a new spanning tree topology. It could also be
used to form a border around part of the network where the root bridge is allowed. (Default:
Disabled)
•
Admin Edge Port – Since end nodes cannot cause forwarding loops, they can pass directly
through to the spanning tree forwarding state. Specifying Edge Ports provides quicker
convergence for devices such as workstations or servers, retains the current forwarding
database to reduce the amount of frame flooding required to rebuild address tables during
reconfiguration events, does not cause the spanning tree to initiate reconfiguration when the
interface changes state, and also overcomes other STA-related timeout problems. However,
remember that Edge Port should only be enabled for ports connected to an end-node device.
(Default: Auto)
•
Enabled – Manually configures a port as an Edge Port.
•
Disabled – Disables the Edge Port setting.
•
Auto – The port will be automatically configured as an edge port if the edge delay time
expires without receiving any RSTP or MSTP BPDUs. Note that edge delay time
(802.1D-2004 17.20.4) equals the protocol migration time if a port's link type is
point-to-point (which is 3 seconds as defined in IEEE 802.3D-2004 17.20.4); otherwise it
equals the spanning tree’s maximum age for configuration messages (see maximum age
under
“Configuring Global Settings for STA”
An interface cannot function as an edge port under the following conditions:
•
If spanning tree mode is set to STP (
), edge-port mode cannot automatically
transition to operational edge-port state using the automatic setting.
•
If loopback detection is enabled (
) and a loopback BPDU is detected, the
interface cannot function as an edge port until the loopback state is released.
•
If an interface is in forwarding state and its role changes, the interface cannot continue to
function as an edge port even if the edge delay time has expired.
•
If the port does not receive any BPDUs after the edge delay timer expires, its role changes
to designated port and it immediately enters forwarding state (see
•
BPDU Guard – This feature protects edge ports from receiving BPDUs. It prevents loops by
shutting down an edge port when a BPDU is received instead of putting it into the spanning
tree discarding state. In a valid configuration, configured edge ports should not receive BPDUs.
If an edge port receives a BPDU an invalid configuration exists, such as a connection to an
unauthorized device. The BPDU guard feature provides a secure response to invalid
configurations because an administrator must manually enable the port. (Default: Disabled)
•
BPDU Filter – BPDU filtering allows you to avoid transmitting BPDUs on configured edge ports
that are connected to end nodes. By default, STA sends BPDUs to all ports regardless of
whether administrative edge is enabled on a port. BDPU filtering is configured on a per-port
basis. (Default: Disabled)
•
Migration – If at any time the switch detects STP BPDUs, including Configuration or Topology
Change Notification BPDUs, it will automatically set the selected interface to forced
STP-compatible mode. However, you can also use the Protocol Migration button to manually
re-check the appropriate BPDU format (RSTP or STP-compatible) to send on the selected
interfaces. (Default: Disabled)