Restrictions and Cautions for Implementing STP

This section presents restrictions and cautions when implementing the different STP versions:

• STP can be enabled on a physical interface using only one of these configurations:

  • Different STP versions are configured within a routing instance of the type virtual-switch. Currently under L2CPD, a virtual switch can only be configured under the default logical-router hierarchy.
  • Creating a routing instance of type layer2-control
  • Different STP versions are configured within the default virtual switch of the default logical system.

• These are the restrictions when STP is enabled on a physical interface within a virtual-switch configuration:

  • No other virtual switch can have logical interfaces on this physical interface.
  • Logical interfaces on this physical interface cannot belong to any routing instance of the type vpls.
  • If other logical interfaces on this physical interface have routing/ccc/tcc enabled, then this traffic is not affected by the STP state of the physical interface.
• Different STP versions are supported on CE interfaces of VPLS routing-instance by creating a routing instance of type layer2-control, which cannot have any bridge domains defined.
• If STP is not configured on a physical interface, the restrictions listed above do not apply. Different logical interfaces on a physical interface can span virtual switches as well as routing instances of the type vpls.
• Virtual switches cannot have any logical interfaces corresponding to physical interfaces that are referenced within a routing instance of the type layer2-control, as shown in the following example configuration.
  routing-instance l2control-4-green {instance-type layer2-control;protocols {rstp {interface ge-1/2/3 ;interface ge-2/2/3 ;interface ge-3/2/4 ;}}}routing-instance green {instance-type vpls ;interface ge-1/2/3.11 ;interface ge-2/2/3.1 ;interface ge-3/2/4.2 ;}
• Any given logical interface of a bridge domain can be associated with only one MSTI. All VLANs that are part of a VLAN range of a logical interface must be associated with the same MSTI. An MSTI must be a super-set of all VLANs that are associated with a logical interface.
• A bridge domain on the MX Series is either associated with a specific VLAN or all VLANs (vlan-all); you cannot use vlan-range. If a bridge domain is configured as vlan-all, it represents multiple broadcast domains, and it can be associated with multiple MSTIs. Each VLAN within vlan-all is an independent and separate broadcast domain.
• If you include the vlan statement within a bridge domain and specify the none option, then MSTP cannot be enabled on physical interfaces corresponding to the logical interfaces defined under the bridge domain.

• MSTP cannot be configured on physical interfaces that have logical interfaces with VLAN translation. MSTP is not allowed within a bridge domain if none of the logical interfaces in the bridge domain has a vlan-range and:

  • All of the logical interfaces in the bridge domain do not have the same VLAN

    OR

  • All of the logical interfaces in the bridge domain have the same VLAN, but the vlan-id defined for the bridge domain is different.
• STP and RSTP can be configured on physical interfaces that have logical interfaces with VLAN translation.

Related Topics

• Decision Sequence for a Loop-Free STP Topology
• Key Concepts in Spanning Tree Protocols
• Multiple Spanning Tree Protocol
• Overview of Spanning Tree Protocol on Juniper Networks MX Series 3D Universal Edge Routers
• Port Roles in STP
• Rapid Spanning Tree Protocol Port States and Port Roles
• Spanning Tree Protocol Operation
• Spanning Tree Protocol States
• STP Scaling and Performance on Juniper Networks MX Series 3D Universal Edge Routers
• VLAN Spanning Tree Protocol