Ethernet Ring Protection Using Ring Instances for Load Balancing
Juniper Network MX Series 5G Universal Routing Platforms support Ethernet ring protection (ERP) to help achieve high reliability and network stability. ERP is used in router or bridge networks to protect against link failure. A single-ring topology is configured that uses one specific link called a ring protection link (RPL) to protect the whole ring. When all links are up and running, the RPL blocks traffic and remains idle. However, if a link fails, the RPL routes traffic to bypass the failure on the ring.
To learn how ERP works in a single-ring topology, see Ethernet Ring Protection.
MX Series routers now support ERP ring instances. Whereas traffic in a single-ring topology follows the same path, traffic within ring instances allows some traffic to pass through one path while other traffic can follow a different path. Dividing traffic in this way supports traffic load balancing in the physical ring.
Ring instances are like traffic channels that contain different sets of virtual LANS (VLANs). A ring instance is responsible for the protection of a subset of VLANs that transport traffic over the physical ring. When ring instances are configured for the ring, each ring instance should have its own RPL owner, an east and a west interface, and a ring protection link end.
Each ring instance has a control channel and a specific data channel. A data channel is a group of bridge domain VLAN IDs. All VLAN IDs within the same ring interface share the same data-forwarding properties controlled by the ERP. If no data channel is defined in the ring configuration, ERP will only operate on the physical link instead of as a ring instance using logical links.
When operating ERP in a topology with other protocols, the following considerations should be observed:
If a physical interface is part of an Ethernet ring, it cannot be configured for Spanning Tree Protocol (STP) or Multiple Spanning Tree Protocol (MSTP).
ERP and Per-VLAN Spanning Tree (PVST) can be configured on the same topology as long as PVST doesn't share the same VLAN with any Ethernet ring instance configured on the physical port.
If ERP is configured only as a physical ring instance (a ring without a data channel) in a topology also configured for PVST, ERP checks the PVST configuration on two ring interfaces and automatically creates a data channel excluding VLANs used by PVST.