Alcatel-Lucent OmniSwitch 6800 Series - Enabling;Disabling the VLAN BPDU Switching Status; Configuring the Path Cost Mode

Configuring Spanning Tree Parameters Configuring STP Bridge Parameters
OmniSwitch 6800/6850/9000 Network Configuration Guide March 2008 page 7-25
Enabling/Disabling the VLAN BPDU Switching Status
By default, BPDU are not switched on ports associated with VLANs that have Spanning Tree disabled.
This may result in a network loop if the VLAN has redundant paths to one or more other switches. Allow-
ing VLANs that have Spanning Tree disabled to forward BPDU to all ports in the VLAN, can help to
avoid this problem.
To enable or disable BPDU switching on a VLAN, enter bridge followed by an existing VLAN ID (or
VLAN 1 if using a flat Spanning Tree instance) then bpdu-switching followed by enable or disable. For
example, the following commands enable BPDU switching on VLAN 10 and disable it on VLAN 20:
-> bridge 10 bpdu-switching enable
-> bridge 20 bpdu-switching disable
Note. Make sure that disabling BPDU switching on a Spanning Tree disabled VLAN will not cause
network loops to go undetected.
Configuring the Path Cost Mode
The path cost mode controls whether the switch uses a 16-bit port path cost (PPC) or a 32-bit PPC. When
a 32-bit PPC switch connects to a 16-bit PPC switch, the 32-bit switch will have a higher PPC value that
will advertise an inferior path cost to the 16-bit switch. In this case, it may be desirable to set the 32-bit
switch to use STP or RSTP with a 16-bit PPC value.
By default, the path cost mode is set to automatically use a 16-bit value for all ports that are associated
with an STP instance or an RSTP instance and a 32-bit value for all ports associated with an MSTP value.
It is also possible to set the path cost mode to always use a 32-bit regardless of which protocol is active.
To change the path cost mode, use the bridge path cost mode command and specify either auto (uses
PPC value based on protocol) or 32bit.(always use a 32-bit PPC value). For example, the following
command changes the default path cost mode, which is automatic, to 32-bit mode:
-> bridge path cost mode 32bit
Note. Cisco supports two default path cost modes: long or short just like in OmniSwitch 1x1 implementa-
tion. If you have configured PVST+ mode in the OmniSwitch, it is recommended that the same default
path cost mode should be configured in the same way in all the switches, so that, the path costs for similar
interface types will be consistent when connecting ports between OmniSwitch and Cisco Switches.