Alcatel Lucent 7750 SR Router High Availability Deployment and Troubleshooting

Alcatel Lucent 7750 SR series business router high availability architecture deployment and operation manual

At the edge of converged IP networks, the Alcatel Lucent 7750 Service Router (SR) series has become the preferred platform for large enterprises, cloud service providers, and operators to build multi service edge networks due to its high switching capacity of up to 9.6 Tbps, 400 Gbps line speed performance brought by FP3 network processors, and high availability features such as Non Stop Routing/On Stop Services. However, the efficient operation of high-performance platforms relies on scientific chassis selection, redundant configuration, routing strategy optimization, and fast fault location capabilities. This article is based on the technical specifications of the 7750 SR series products, systematically sorting out the troubleshooting process from hardware selection, high availability architecture deployment, L2/L3 VPN business configuration to common alarm and performance degradation scenarios in daily operation and maintenance, providing IP/MPLS network engineers with a practical reference that can be directly implemented.

Product Family Overview and Selection Decision

The 7750 SR series offers three chassis forms, covering different capacity requirements from regional aggregation to the core edge:

7750 SR-7:8U height, 5 I/O module slots, exchange capacity of 2 Tbps, throughput of 2976 Mpps. Supports up to 5 100GbE ports or 15 40GbE ports or 100 10GbE ports. Suitable for medium-sized aggregation nodes or enterprise edges.

7750 SR-12:14U height, 10 I/O module slots, exchange capacity of 4 Tbps, throughput of 5952 Mpps. Supports up to 10 100GbE ports, 30 40GbE ports, or 200 10GbE ports. Suitable for large metropolitan area edges or regional cores.

7750 SR-12e: 22U height, 9 I/O module slots (but supports higher density cards), switching capacity of 9.6 Tbps, throughput of 10713.6 Mpps. Supports up to 9 100GbE ports, 27 40GbE ports, or 180 10GbE ports. Suitable for backbone edge and high-density interconnection scenarios.

Core considerations for selection:

Slot and Scalability: Although SR-12e has fewer I/O slots than SR-12 (9 vs 10), its backplane bandwidth is larger and supports higher density 100G cards. If 100G is the main choice in the future, SR-12e will be given priority.

Main control redundancy: All models support dual SF/CPM (Switching and Control Processor Module) redundancy, equipped with Cavium 10 core 1.5 GHz processor and 16 GB DDR3 memory, with default dual Compact Flash storage.

Power supply and heat dissipation: Supports AC/DC redundant power supply, SR-7 and SR-12 are side to rear air ducts, and SR-12e is front to rear air duct, which needs to be matched with the airflow organization in the computer room. The full weight is 70.5 kg, 155.7 kg, and 249.5 kg respectively, and the rack load capacity needs to be confirmed during installation.

Hardware architecture and board type

The 7750 SR adopts a distributed forwarding architecture, where the data plane and control plane are separated to ensure that a failure in one plane does not affect the operation of another plane.

Key components:

SF/CPM (Switching and Control Processor Module): integrates switching matrix and control processing functions. SR-7/12/12e both support dual SF/CPM redundancy, and Non Stop Routing technology is used to maintain protocol sessions during primary and backup switching.

IMM (Integrated Media Module): an integrated line card that integrates FP3 network processors and physical ports. Common models include:

1×100GbE CFP + 10×10GbE SFP+ IMM

3×40GbE QSFP+ + 20×GbE SFP IMM

20×10GbE SFP+ IMM

48×GbE SFP IMM

IOM (Input/Output Module): Similar to IMM, but with slightly lower processing power, typically used for early deployment. It is recommended to directly use IMM for new facilities to achieve optimal performance.

CFP/QSFP+/SFP+optical module: supports full speed from gigabit to 100G, specific models include JL153A（100GBASE‑LR4）、JL155A（40GBASE‑LR4）、JL156A（10GBASE‑SR） Wait, covering short-range multimode to long-range single-mode.

Port density calculation: For example, when SR-12e is equipped with 9 blocks of 1 × 100G+10 × 10G IMM, it can provide 9 100G ports and 90 10G ports; If equipped with a 48 × GbE IMM, it can provide 432 Gigabit ports.

High availability feature deep configuration

The high availability mechanism of 7750 SR is its core competitive advantage, far surpassing simple hardware redundancy.

3.1 Non‑Stop Routing（NSR）

In the event of a control plane failure (such as a primary SF/CPM crash), the backup SF/CPM seamlessly takes over without relying on adjacent routers to assist in recovery.  

Configuration points:

Ensure that both SF/CPMs are installed and in a "hot standby" state (show redundancy shows HA state: hot standby).

Enable NSR: Add the non stop routing command under routing protocol configuration.

Regularly perform manual switching tests (admin redundancy switchover) to verify the backup master control function.

3.2 Non‑Stop Services（NSS）

On the basis of NSR, NSS ensures that the status of VPLS, VLL, IP VPN and other services is not affected during the switching process. The backup master maintains the business forwarding table and session status, and ensures that the business does not lose packets after switching (or packet loss occurs at the sub second level).