Cisco ASR9000 Fabric Troubleshooting: Show Commands

Packet drops on a Cisco ASR 9000 running IOS XR can live anywhere along the data path: ingress NPU, bridge ASIC, fabric interface ASIC (FIA), crossbar or egress linecard. Cisco's service-provider knowledge base documents a structured method to isolate fabric-related drops using a specific set of show commands, and this article walks that procedure from clearing counters to reading NPU and FIA statistics.

Know Your Linecard: Trident vs Typhoon

Trident-based cards (A9K-40GE, A9K-2T20G, A9K-4T, A9K-8T/4, A9K-8T, A9K-16T/8) have a bridge ASIC between the NPU and the FIA, while Typhoon cards (A9K-24x10, A9K-36x10, A9K-MOD80/160, A9K-2x100) carry a linecard fabric stage to reduce fabric link count. The forwarding architecture differs but the troubleshooting commands are the same.

Step 1: Look for Active PFM Alarms

RP/0/RSP0/CPU0:router# show pfm location all

Pay attention to alarms such as %PLATFORM-PFM_NP-0-TMA_CLUSTER_PARITY (hardware error) and %PLATFORM-DIAGS-3-PUNT_FABRIC_DATA_PATH_FAILED (diag packets not returned by NP hardware).

Step 2: Check Hardware FPGA Versions

RP/0/RSP0/CPU0:router# show controllers np summary all
RP/0/RSP0/CPU0:router# admin show hw-module fpd all location all

On Trident linecards, ensure the bridge FPGA revision is above 0.41 for 40G cards and above 0.5 for 80G cards to avoid known memory errors.

Step 3: Clear All Counters Before Testing

RP/0/RSP0/CPU0:router# clear counters all
RP/0/RSP0/CPU0:router# clear controller np counters all
RP/0/RSP0/CPU0:router# clear controller fabric fia location
RP/0/RSP0/CPU0:router# clear controller fabric crossbar-counters location

Then start the traffic pattern that caused the drop and walk the path.

Step 4: Walk the Data Path

! input interface counters
RP/0/RSP0/CPU0:router# show interfaces tenGigE 0/1/0/0

! NPU counters
RP/0/RSP0/CPU0:router# show controllers np counters all location

! NPU to interface mapping
RP/0/RSP0/CPU0:router# show controllers np ports all

! NPU - bridge fabric counters per NPU
RP/0/RSP0/CPU0:router# show controllers np fabric-counters all np0 location

Key NPU counters: 800 PARSE_ENET_RECEIVE_CNT (packets from external interface), 970 MODIFY_FABRIC_TRANSMIT_CNT (packets sent to fabric), 801 PARSE_FABRIC_RECEIVE_CNT (from fabric), 971 MODIFY_ENET_TRANSMIT_CNT (to external interface). Compare them to find where packets stop moving.

Understanding the Fabric Architecture

• Octopus - the Trident fabric interface ASIC on the linecard and RSP.
• SCZ (Santa Cruz) - the actual fabric chip, two on the RSP4/RSP440.
• BE (Bellagio) - the fabric arbiter granting access to the crossbar; both arbiters see every request, so failover is seamless.

The RSP punts and fabric paths share the same FIA, so RSP failures and fabric problems can look identical from the interface - the counter walk above separates them.

Related articles: Cisco IOS XR configuration management, Cisco Nexus NX-OS VLAN and trunk configuration, and Data center ToR switch selection.

原文链接：https://community.cisco.com/t5/service-providers-knowledge-base/asr9000-xr-understanding-the-fabric-and-troubleshooting-commands/tac-p/3812960