Chapter 7 Configuring STP and RSTP on the ML-Series Card

RSTP Features

Accelerated Aging to Retain Connectivity

The default for aging dynamic addresses is 5 minutes, which is the default setting of the bridge bridge-group-numberaging-timeglobal configuration command. However, a spanning-tree reconfiguration can cause many station locations to change. Because these stations could be unreachable for 5 minutes or more during a reconfiguration, the address-aging time is accelerated so that station addresses can be dropped from the address table and then relearned.

Because each VLAN is a separate spanning-tree instance, the switch accelerates aging on a per-VLAN basis. A spanning-tree reconfiguration on one VLAN can cause the dynamic addresses learned on that VLAN to be subject to accelerated aging. Dynamic addresses on other VLANs can be unaffected and remain subject to the aging interval entered for the switch.

RSTP Features

RSTP provides rapid convergence of the spanning tree. It improves the fault tolerance of the network because a failure in one instance (forwarding path) does not affect other instances (forwarding paths). The most common initial deployment of RSTP is in the backbone and distribution layers of a Layer 2 switched network; this deployment provides the highly available network required in a service-provider environment.

RSTP improves the operation of the spanning tree while maintaining backward compatibility with equipment that is based on the (original) IEEE 802.1D spanning tree.

RSTP takes advantage of point-to-point wiring and provides rapid convergence of the spanning tree. Reconfiguration of the spanning tree can occur in less than 2 second (in contrast to 50 seconds with the default settings in the IEEE 802.1D spanning tree), which is critical for networks carrying delay-sensitive traffic such as voice and video.

These sections describe how RSTP works:

•Supported RSTP Instances, page 7-9

•Port Roles and the Active Topology, page 7-10

•Rapid Convergence, page 7-11

•Synchronization of Port Roles, page 7-12

•Bridge Protocol Data Unit Format and Processing, page 7-13

•Topology Changes, page 7-14

Supported RSTP Instances

The ML Series supports per-VLAN rapid spanning tree (PVRST) and a maximum of 255 rapid spanning-tree instances.

Caution At more than 100 RSTP instances the RSTP instances may flap and may result in MAC entries flushed, and MAC entries learned again and again. This will cause flooding in the network. So it is recommended to keep the RSTP instances to be less than 100, to keep system from being unstable.

Cisco ONS 15310-CL, ONS 15310-MA, and ONS 15310-MA SDH Ethernet Card Software Feature and Configuration Guide, R9.1 and R9.2

 

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ONS 15310-CL, ONS 15310-MA, Cisco ONS 15310-MA specifications

Cisco Systems has long been a leader in networking and telecommunications technology, and among its impressive lineup of products, the Cisco ONS 15310 series stands out as an essential solution for optical networking. This series includes models such as the ONS 15310-MA, ONS 15310-CL, and ONS 15310-CA, each designed to meet the diverse needs of service providers and enterprises seeking to enhance their optical transport networks.

The Cisco ONS 15310-MA is an advanced multi-service platform designed for metropolitan area networks. It facilitates the seamless transport of data, voice, and video over optical networks. One of its main features is its ability to support a variety of interfaces, including Ethernet, SONET/SDH, and Wavelength Division Multiplexing (WDM), allowing users to integrate multiple services into a single platform. Additionally, the ONS 15310-MA supports advanced traffic management and Quality of Service (QoS) features to prioritize critical applications and ensure consistent performance.

The ONS 15310-CL variant is tailored for more specific applications, providing enhanced capabilities aimed at delivering carrier-grade services. It features a robust architecture that accommodates high-capacity traffic without compromising reliability. This model emphasizes low power consumption and a compact design, making it suitable for deployment in space-constrained environments. The ONS 15310-CL also supports a wide range of optical interfaces, making it highly flexible for various network configurations.

In terms of technologies, the Cisco ONS 15310 series leverages Optical Transport Network (OTN) capabilities, providing high efficiency and greater bandwidth utilization. OTN technology enables efficient error correction and adds resilience to the network through its built-in protection mechanisms. Furthermore, the series supports seamless integration with existing IP/MPLS networks, creating a cohesive infrastructure as organizations evolve their networking requirements.

One of the defining characteristics of the ONS 15310 series is its focus on scalability. Network operators can start with a modest deployment and gradually expand capacity as demand grows. This adaptability is complemented by Cisco's comprehensive management and monitoring tools, providing operators with real-time insights into network performance and facilitating proactive management.

In conclusion, the Cisco ONS 15310-MA and ONS 15310-CL models represent sophisticated solutions for modern optical networks. With their versatile features, advanced technologies, and robust design, they empower service providers and enterprises to build resilient, high-capacity networks that meet the demands of today’s data-driven world.
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