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Setting up sampled Netflow on the Nexus 6000 series software version 6.x

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Introduction

Setting up sampled Netflow on the Nexus 6000 series software version 6.x. 

User would like to know if there a document which shows how to set up sampled Netflow, 'feature netflow', unable to locate it on the Nexus 6001 software 6.x.

Solution

Only 7.x support sampled netflow and not version 6.x. The Sampled NetFlow feature samples incoming packets on an interface. The packets sampled then qualify to create flows. Sampled NetFlow reduces the amount of export data sent to the collector by limiting the number of packets that create flows and the number of flows. It is essential when flows are created on a line card or external device, instead of on the forwarding engine.

New Software Features in Cisco NX-OS Release 7.0(0)N1(1)
Cisco NX-OS Release 7.0(0)N1(1) is a major release that includes bug fixes and the following software features and enhancements:

  • Anycast HSRP
  • Data Analytics
  • Dynamic Fabric Automation
  • Early Warning for FIB Exhaustion
  • ECN with WRED
  • ERSPAN with ACL Filtering
  • FabricPath Operations, Administration, and Management
  • Intermediate System to Intermediate System Protocol
  • Layer 2 Bidirectional Forwarding Detection
  • Multi-Destination Switch Port Analyzer
  • Multi-Destination Tree
  • OpenFlow v1.0
  • Overload Bit
  • Port Channel Max Links
  • Q-in-Q VLAN Tunneling
  • Sampled NetFlow
  • Switch Port Analyzer with ACL Filtering
  • Static/Dynamic Network Address Translation
  • TCAM Carving
  • VN-Segment

Sampled NetFlow

Cisco NX-OS supports sampled NetFlow. This feature samples incoming packets on an interface. The packets sampled then qualify to create flows. Sampled NetFlow reduces the amount of export data sent to the collector by limiting the number of packets that create flows and the number of flows. It is essential when flows are created on a line card or external device, instead of on the forwarding engine.
 
The sampling mode supported is M out of N (M:N), where M packets are selected randomly out of every N packets for sampling, and only those packets can create flows. The lowest possible sampling rate on the Cisco Nexus 6000 series is 1:64K packets. The following table shows the different packet rates for different port types when the sampling rate is set to 1:64K packets:
 
Port SpeedNumber of packets using a 1:64K sampled packet rate
1 Gigabit23
10 Gigabit230
40 Gigabit920
Note
The values in the above table apply to 64 Byte sized packets. The values are different for different size of packets.
 

More Information

Nexus 6000 provides Smart Buffering such as shared buffering for making efficient usage of the buffer for burst absorption. Nexus 6000 also provides Intelligent Flow Management such as Sampled Netflow for traffic engineering, capacity planning or Priority Flow Control for point-to-point flow control of Ethernet traffic based on IEEE 802.1p CoS. With a flow-control mechanism in place, congestion does not result in drops, transforming Ethernet into a reliable medium. Explicit congestion notification also allows an end-to-end notification of network congestion without dropping packets.
 

Reference

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