The Journey of a Network Engineer

May 16 2011   12:49PM GMT

What is the difference between M1 and F1 Cisco Nexus Line cards?

Sulaiman Syed Profile: Sulaiman Syed

Cisco Nexus series switches brought a new technology to the data center. The whole designed is changed from the Catalyst 6500 series. Nexus is no longer dependent on SUP’s backplane, it is more like a midplane architecture. Let me elaborate a little on this, what that statement means that currently if there is any limitation of speed, then it is posed by the Line Card. Then how the Line cards communicate with each other, they do with Fabric Modules. Read for further details into basic architecture difference between Catalyst 6500 vs Nexus 7000

Nexus Line card modules fall into two major categories. M1, and F1. There is another variation to the M1 which is M1-XL. Brad Hedlund wrote a good article that can be referenced for reading, titled “Cisco Nexus 7000 connectivity solutions for Cisco UCS

M1, M1-XL

M1 Series were the introductory line cards that were offered by Cisco for Nexus. They come with a fabric of 80GB. These cards have 10Gig links making them ideal for Distribution layer. Lets put down the specifications or performance Metrics from the data sheets. These cards provide the Layer 2 and Layer 3 connectivity! You can always multiply these numbers with the maximum line cards possible to install into a chassis to get the marketing figures.
1- Delivery at 60 Million Packets per second (Mpps) for layer 2,3 IPv4.
2- Delivery at 30 Mpps IPv6 unicast.
3- Delivery of Access Control List (ACL) to 64k entries per module. The entries include address of Layer 2,3,4 and Cisco’s Metadata fields- security group tags (SGTs)
4- in 32 Port line card, each 4 ports share 10GB of Fabric. They can run either 1 port 10GIG disable 2,3, and 4 OR all 4 in shared mode.
5- Memory 1GB DRAM
6- Network management: Cisco DCNM 4.0
7- Mac addresses table size of 128k entry
8- FIB table of 128k entry
9- Netflow supports 512k Entry in both Ingres and Egress
10- 16384 bridge domains and 4096 vlan per Virtual Device Context (VDC)
11- Policers of 16k entry

M1-XL Series offers the flexibility or the performance to be internet-facing deployment with wider transceivers module support. What it basically offers the possibility of larger FIB. This can be seen from the following:
* up to 1M IPv4 routes (depending on prefix distribution)
* up to 350k IPv6 routes (depending on prefix distribution)

This was not possible in the M1 Line Cards. M1-XL does provide extra ACL entries support compared to M1, which increased DRAM
1- Memory 2GB DRAM
2- Delivery of Access Control List (ACL) to 128k entries per module.
3- Network management: Cisco DCNM 5.1

F1 Series Line Cards were introduced after the M1. They provide a slight cheaper and more port density with ONLY layer 2 forwarding. This makes an ideal Line card for Access layer. What happens if layer three processing is required? The Line card will forward that traffic to M1, M1-XL cards for processing. These cards have Fabric of 230 GB.

1- 480 Mpps layer two forwarding
2- Delivery of Access Control List (ACL) to 32k entries per module. The entries include address of Layer 2,3,4 and Cisoc’s Metadata fields- security group tags (SGTs)
3- in 32 Port line card with 230GB of fabric.
4- Memory 1GB DRAM
5- Network managment: Cisco DCNM 5.1
6- Mac addresses table size of 16k entry per forwarding engine.

The forwarding engine is something new. Every two ports are connected by a switch on chip. (SoC), these SoC are the forwarding engine. So each SoC supports 16k. What this implies (How marketing figured came) that for 32 port, we have 16 SoC. With careful planning, if we use one VLAN per SoC we get total of 256k of Mac address support. But if we span one vlan among all SoC then we are bounded by max limit of 16k MAC entry.

These cards have the Cisco FiberPath Technology. From the data sheet

The benefits of Cisco FabricPath include:

• Operational simplicity: Cisco FabricPath embeds an autodiscovery mechanism that does not require any additional platform configuration. By offering Layer 2 connectivity, this “VLAN anywhere” characteristic simplifies provisioning and offers workload flexibility across the network.

• High resiliency and performance: Since Cisco FabricPath is a Layer 2 routed protocol, it offers stability, scalability, and optimized resiliency along with network failure containment.

• Massively scalable fabric: By building a forwarding model on 16-way ECMP, Cisco FabricPath helps prevent bandwidth bottlenecks and allows capacity to be added dynamically, without network disruption.

They also have the ability to connect FCoE. these features include
1-Virtual Sans (VSANs)
2-Inter-VSAN Routing
3-PortChannels (UP to 16 links)
4- Storage VDC.

This sums up what I found. I would include or add more things later as I learn or gather them.

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