Routed CO dual homing is a solution that allows seamless failover between nodes for all models of routed CO. In the dual homed environment, only one node forwards downstream traffic to a specific subscriber at a time. Dual homing involves several components:
Redundant Interface
This is used to shunt traffic to the active node for a specific subscriber for downstream traffic.
SRRP
This is used to monitor the state of connectivity to the DSLAM. See the SRRP section for more detail.
MCS
This is used to exchange subscriber host and SRRP information between the dual homed nodes.
Routed CO dual homing can be configured for both wholesaling models. Dual homing is configured by creating a redundant interface that is associated with the protected group interfaces. The failure detection mechanism can be SRRP. If SRRP is used, each node monitors the SRRP state to determine the priority of its own interface.
Dual homing is used to aggregate a large number of subscribers to support a redundancy mechanism that allows a seamless failover between nodes. Because of the Layer 3 nature of the model, forwarding is performed for the full subscriber subnet.