Date created: Friday, December 1, 2017 10:29:45 AM. Last modified: Thursday, April 28, 2022 2:44:58 PM

ASR9901 Specific Hardware Overview


The Cisco ASR9901 codename "Starlord" is a fixed 2u router with no support for any MPAs. It has 2x 100G QSFP28 ports, 24x dual rate 10G/1G SFP+ ports and 16x 1G SFP ports. The ASR9901 has two Tomahawk NPUs, each with 12GBs of forwarding plane memory, with a shared external TCAM (80 Mbit total, 40Mbit per NPU). It is effectively a single SE- Tomahawk line card, in a fixed chassis, with a single RSP.

Each NPU has 8x1G ports, 12x 10G/1G ports and 1x 100G port. Tomahawk NPUs are rated for 240Gbps full duplex, 2x240Gbps == 480Gbps full duplex. However, the ASR9901 "only" has 456Gbps of port capacity so the box should be able to reach full line rate across all ports simultaneously. It actually can't though, as per a standard ASR9K Tomahawk line-card layout (see RSPs/RP/NPUs) each Tomahawk NPU contains a Traffic Manager which "only" operates at 200Gbps full duplex, meaning the TMs actually limit the throughput per NPU to 200Gbps FD.

Both the fixed line card and RSP use an Intel 4-core Broadwell running at 2.4 GHz for the control plane, with the RSP having 32GBs of RAM and the LC having 16GBs. They communicate over an EOBC link.

The 1/10 Gbps SFP+ ports need to be statically configured to operate at either 1 or 10 Gbps speed. This must be done in groups in accordance with the following rules:

  • If the first port in a group of 12 is configured to run at 1 Gbps, all 12 ports in that particular group must run at 1 Gbps.
  • If the first port in a group of 12 is configured to run at 10 Gbps, each group of four ports can be configured to run at either 1 or 10 Gbps. All ports in a group of four must run at the same speed.

The ASR9901 supports the 64-bit version of IOS-XR ("eXR") only.

The ASR9901 supports front to back air flow, redundant power and fan trays. The "downside" is that the power consumption is typically in the 1200W range.