Brocade BigIron RX Series Configuration Guide - Manual (Page 424)

346 BigIron RX Series Configuration Guide
53-1002484-04
PVST/PVST+ compatibility
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For the port to also support the other VLANs (the PVST+ VLANs) in tagged mode. The port must be
a dual-mode port.
The untagged frames are supported on the port’s native VLAN. By default, the native VLAN is the
same as the device’s default VLAN
1
, which by default is VLAN 1. Thus, to support IEEE 802.1Q in a
typical configuration, the port must be able to send and receive untagged frames for VLAN 1 and
tagged frames for the other VLANs.
If you want to use tagged frames on VLAN 1, you can change the default VLAN ID to an ID other
than 1. You also can specify the VLAN on which you want the port to send and receive untagged
frames (the native VLAN). The Port Native VLAN ID does not need to be the same as the default
VLAN.
NOTE
Support for the IEEE 802.1Q spanning tree always uses VLAN 1, regardless of whether the devices
are configured to use tagged or untagged frames on the VLAN.
Enabling PVST+ support
PVST+ support is automatically enabled when the port receives a PVST BPDU. You can manually
enable the support at any time or disable the support if desired.
If you want a tagged port to also support IEEE 802.1Q BPDUs, you need to enable the dual-mode
feature on the port. The dual-mode feature is disabled by default and must be enabled manually.
A port that is in PVST+ compatibility mode due to auto-detection reverts to the default MSTP mode
when one of the following events occurs:
• The link is disconnected or broken
• The link is administratively disabled
• The link is disabled by interaction with the link-keepalive protocol
This allows a port that was originally interoperating with PVST+ to revert to multiple spanning tree
when connected to a device.
Enabling PVST+ support manually
To immediately enable PVST+ support on a port, enter commands such as the following.
BigIron RX(config)# interface ethernet 1/1
BigIron RX(config-if-e1000-1/1)# pvst-mode
Syntax: [no] pvst-mode
NOTE
If you disable PVST+ support, the software still automatically enables PVST+ support if the port
receives a BPDU with PVST+ format.
Displaying PVST+ support information
To display PVST+ information for ports on a device, enter the following command at any level of the
CLI.
1. Cisco PVST/PVST+ documentation refers to the Default VLAN as the Default Native VLAN.