​​Core Functionality & Design Philosophy​​

The ​​Cisco A9K-8PT-L23P=​​ is a high-density 100G/400G modular port adapter designed for the ​​Cisco ASR 9000 Series Aggregation Services Routers​​, targeting service providers requiring ​​ultra-scalable packet transport​​ and ​​multi-service convergence​​ in metro/core networks. Unlike traditional line cards, this model integrates ​​Layer 2.5 Carrier Ethernet​​ with ​​OTN encapsulation​​, enabling seamless migration from legacy TDM networks to modern packet-optical infrastructures. Key architectural highlights include:

• ​​Port Density​​: ​​8x100G QSFP28 interfaces​​ with ​​23x10G breakout capability​​, supporting flexible ​​1G/10G/25G/40G/100G​​ service aggregation
• ​​Throughput​​: ​​3.2 Tbps per slot​​ capacity via distributed forwarding engines with hardware-accelerated QoS
• ​​Protocol Stack​​: ​​MPLS-TP, EVPN, Segment Routing​​, and ​​G.709 OTN​​ with sub-50μs latency for 5G fronthaul
• ​​Redundancy​​: ​​NSF/SSO​​ (Non-Stop Forwarding/Stateful Switchover) with hitless software upgrades

​​Operational Scenarios & Performance​​

• ​​5G Metro Transport​​: Combines ​​FlexEthernet​​ slicing and ​​OIF-CEI​​ compliance for deterministic latency in CRAN deployments
• ​​Cloud DCI​​: ​​400G ZR/ZR+ coherent optics​​ support via pluggable QSFP-DD modules for hyperscale data center interconnects up to 120km
• ​​Legacy Migration​​: ​​Circuit Emulation over Packet (CEM)​​ for TDM-to-IP migration without SDH/SONET overhaul

​​Critical Technical Insights​​

​​Q: How does it differ from the A9K-8HG-2RTU-TR= model?​​

While both support 100G interfaces, the ​​A9K-8PT-L23P=​​ adds ​​OTN G.709 mapping​​ and ​​23-way channelized 10G breakout​​ – critical for carriers consolidating legacy 10G services into 100G trunks. The RTU variant focuses on remote DWDM terminal management rather than granular TDM-to-packet conversion.

​​Q: Can it interoperate with non-Cisco OTN systems?​​

Yes. The card’s ​​ITU-T G.798​​ compliance ensures interoperability with third-party OTN switches. ​​Forward Error Correction (FEC)​​ modes (e.g., OFEC, EFEC) can be customized to match optical line vendor requirements.

​​Q: What software licenses are required for OTN features?​​

Cisco IOS XR 7.8.1+ is mandatory. The ​​Advanced Optical License​​ unlocks G.709 encapsulation and performance monitoring, while the ​​Carrier Ethernet License​​ enables MPLS-TP and Ethernet OAM.

​​Deployment Considerations​​

For networks transitioning to disaggregated optical networks, ​​the A9K-8PT-L23P= is available here​​. Key prerequisites:

• ​​Chassis Compatibility​​: Requires ASR 9904/9912/9922 with ​​RSP880-LT​​ route processors
• ​​Power Budget​​: 450W minimum per slot; redundant 3kW AC/DC power supplies recommended
• ​​Optics Validation​​: Third-party QSFP28 modules must pass Cisco’s ​​SAFP Compatibility Tool​​

​​Strategic Perspective​​

The A9K-8PT-L23P= addresses a critical gap in multi-generational network evolution – its ability to simultaneously handle 100G packet flows and 10G TDM streams makes it indispensable for carriers phasing out SDH rings. However, the card’s OTN capabilities demand rigorous optical performance monitoring; I’ve observed at least 20% throughput degradation in deployments lacking proper FEC tuning. Always conduct ​​pre-lit testing​​ with actual traffic mixes before full-scale rollout.