Stp Rules And Restrictions - Extreme Networks ExtremeWare XOS Command Reference Manual

ExtremeWare XOS 11.5 supports only the Summit X450 family of switches and the BlackDiamond 8800 series switch.
STP Commands
Extreme Multiple Instance Spanning Tree Protocol (EMISTP) mode
●
EMISTP mode is proprietary to Extreme Networks and is an extension of STP that allows a physical
port to belong to multiple STPDs by assigning the port to multiple VLANs. EMISTP adds significant
flexibility to STP network design. BPDUs are sent with an 802.1Q tag having an STPD instance
Identifier (StpdID) in the VLANid field.
This encapsulation mode supports the following STPD modes of operation: 802.1D and 802.1w.
Per VLAN Spanning Tree (PVST+) mode
●
This mode implements PVST+ in compatibility with third-party switches running this version of STP.
The STPDs running in this mode have a one-to-one relationship with VLANs, and send and process
packets in PVST+ format.
This encapsulation mode supports the following STPD modes of operation: 802.1D and 802.1w.
These encapsulation modes are for STP ports, not for physical ports. When a physical port belongs to
multiple STPDs, it is associated with multiple STP ports. It is possible for the physical port to run in
different modes for different domains to which it belongs.
MSTP STPDs use only 802.1D BPDU encapsulation mode. The switch prevents you from configuring
EMISTP or PVST+ encapsulation mode for MSTP STPDs.

STP Rules and Restrictions

This section summarizes the rules and restrictions for configuring STP as follows:
The carrier VLAN must span all ports of the STPD. (This is not applicable to MSTP.)
●
The StpdID must be the VLANid of the carrier VLAN; the carrier VLAN cannot be partitioned. (This
●
is not applicable to MSTP.)
A default VLAN cannot be partitioned. If a VLAN traverses multiple STPDs, the VLAN must be
●
tagged.
An STPD can carry, at most, one VLAN running in PVST+ mode, and its StpdID must be identical
●
with that VLANid. In addition, the PVST+ VLAN cannot be partitioned.
The default VLAN of a PVST+ port must be identical with the native VLAN on the PVST+ device
●
connected to that port.
If an STPD contains both PVST+ and non-PVST+ ports, that STPD must be enabled. If that STPD is
●
disabled, the BPDUs are flooded in the format of the incoming STP port, which may be incompatible
with those of the connected devices.
The 802.1D ports must be untagged; and the EMISTP/PVST+ ports must be tagged in the carrier
●
VLAN.
An STPD with multiple VLANs must contain only VLANs that belong to the same virtual router
●
instance.
Automatically adding ports to an STPD (known as STP autobind) cannot be configured on a
●
Netlogin VLAN.
STP cannot be configured on the following ports:
●
A mirroring target port.
■
A software-controlled redundant port.
■
A Netlogin port.
■
MSTP and 802.1D STPDs cannot share a physical port.
●
Only one MSTP region can be configured on a switch.
●
1166
ExtremeWare XOS 11.5 Command Reference Guide