Related Documentation
- EX, MX Series
- VPLS Multihomed Layer 2 Ring and MPLS Infrastructure Topology
- Configuring VPLS Root Protection Topology Change Actions to Control Global Spanning Tree Behavior
- Configuring VPLS Root Protection Topology Change Actions to Control VLAN Spanning Tree Behavior
- MX Series
- Example: Configuring VPLS Root Topology Change Actions
VPLS Multihomed Layer 2 Ring and MPLS Infrastructure Overview
Redundancy is built into many networks through the use of alternate links and paths, which often take the shape of rings.
In the case of multiple hosts attached to customer edge (CE) routers and provider edge (PE) routers to secure virtual private LAN service (VPLS), this practice is often called multihoming:
- Multiple hosts attach to CE routers, which are attached to each other as well as to the PE routers that access the VPLS network cloud. Any single link between the edge routers can fail without impacting the hosts’ access to the VPLS services.
- This Layer 2 ring connects to the multiprotocol link switching (MPLS) infrastructure through two PE routers. Link breaks on the ring are protected by running a version of the spanning-tree protocol with the root-protect option enabled.
The virtual private network (VPN) protocols at Layer 3, however, are not aware of the blocking state that results from this root protection setup (rings or loops are not permitted at Layer 2 because the Layer 2 protocols will not function properly).
However, to keep the Layer 2 ring functioning in a multihomed environment with link failures, the spanning-tree protocol running on the MX Series routers requires the following additional configuration:
- The VPN protocols have to act on the blocking and unblocking of interfaces by the spanning-tree protocol. Specifically, media access control (MAC) flush messages need to be sent by the blocking PE router to LDP peers in order to flush the MAC addresses learned when other interface ports were blocked.
- Also, if an active PE router with VPLS root protection bridging enabled loses VPLS connectivity, root protection requires that the bridge switch to the other PE router to maintain connectivity. The spanning-tree protocol needs to be aware of the status of the VPLS connectivity on the PE router. If the MAC address cache is not flushed when the topology changes, frames could be sent to the wrong device.
You can control the actions taken by the MX Series router when the topology changes in a multihomed Layer 2 ring VPLS environment using VPLS root protection.
Related Documentation
- EX, MX Series
- VPLS Multihomed Layer 2 Ring and MPLS Infrastructure Topology
- Configuring VPLS Root Protection Topology Change Actions to Control Global Spanning Tree Behavior
- Configuring VPLS Root Protection Topology Change Actions to Control VLAN Spanning Tree Behavior
- MX Series
- Example: Configuring VPLS Root Topology Change Actions
Published: 2013-04-01
Related Documentation
- EX, MX Series
- VPLS Multihomed Layer 2 Ring and MPLS Infrastructure Topology
- Configuring VPLS Root Protection Topology Change Actions to Control Global Spanning Tree Behavior
- Configuring VPLS Root Protection Topology Change Actions to Control VLAN Spanning Tree Behavior
- MX Series
- Example: Configuring VPLS Root Topology Change Actions
