Overview

The 7210 SAS supports the grouping together, or stacking, of a set of nodes to create a virtual chassis (VC). The following nodes can be stacked to form a VC:

• the 7210 SAS-Sx 1/10GE and its variants

• the 7210 SAS-S 1/10GE and its variants

A VC provides operational simplicity because it uses a single IP address and MAC address for a set of stacked nodes. This set of nodes can be provisioned and monitored as a single platform rather than as individual nodes. For example, users can provision services for all ports in the VC without having to log in and access each node individually. As well, the NSP NFM-P management system can manage and monitor the VC as a single platform rather than the individual nodes that comprise it.

In addition to operational simplicity, a VC increases service reliability by providing redundancy in the following ways:

• If the node running control plane protocols in the VC fails, a standby node takes over the master node function, minimizing service loss.

• Access devices can be connected using a mechanism such as LAG or G.8032 so that the impact of a node failure in a VC is minimized for services on the access device.

Nodes can be added to or removed from a VC to increase the total available ports or to replace a failed unit.

The nodes of the VC are connected through their stacking ports. The total capacity provided by the stacking ports is equivalent to the sum of the bandwidth provided by the individual port. The stacking ports are used for forwarding service traffic and for exchanging management and control messages between the nodes in the VC. The VC control traffic is prioritized over other traffic on the stacking ports.

The 7210 SAS supports VC in standalone mode.

Nodes in the VC can take on the role of active CPM, standby CPM, or line card (also known as an IMM). In a VC, two of the nodes can be designated as CPM nodes (along with a built in IMM) and the other node is designated as an IMM-only node. See Node roles in the VC for more information. Each of the nodes in the VC is provisioned as a card, similar to the cards in a chassis.

A VC can support uplink over-subscription, where only a few uplinks from the end nodes of the stack are connected to the network, and all customer services are delivered through these uplink ports.

A VC can also support a configuration where the uplinks are not over-subscribed and operators can connect any number of ports from each node in the stack to the network core. In Release 11.0, the VC software module keeps track of the shortest path from a specific source IMM to a destination IMM and uses it to forward packets through the stack using the stacking ports.

A VC can operate as a Layer 2 device, where only VLANs are used for uplink connectivity, or as a full-fledged IP/MPLS platform with support for IP/MPLS-based Layer 2 and Layer 3 VPNs.