The NetFlow cache on the PFC captures statistics for flows routed in hardware.

The PFC uses one of these flow masks to create NetFlow entries:

• source-only --The cache contains one entry for each source IP address. All flows from a given source IP address use this entry.
• destination --The cache contains one entry for each destination IP address. All flows to a given destination IP address use this entry.
• destination-source --The cache contains one entry for each source and destination IP address pair. All flows between the same source and destination IP addresses use this entry.
• destination-source-interface --Adds the source VLAN SNMP ifIndex to the information in the destination-source flow mask.
• full --A separate cache entry is created for each IP flow. A full entry includes the source IP address, destination IP address, protocol, and protocol interfaces.
• full-interface --Adds the source VLAN SNMP ifIndex to the information in the full flow mask.

For all NetFlow export versions, the NetFlow export datagram consists of a header and a sequence of flow records. The header contains information such as sequence number, record count, and system uptime. The flow record contains flow information, such as IP addresses, ports, and routing information.

NetFlow version 9 export format is the newest NetFlow export format. The distinguishing feature of the NetFlow version 9 export format is that it is template based. Templates make the record format extensible. NetFlow version 9 export format allows future enhancements to NetFlow without requiring concurrent changes to the basic flow-record format.

The NetFlow version 9 export record format is different from the traditional NetFlow fixed format export record. In NetFlow version 9, a template describes the NetFlow data, and the flow set contains the actual data. This arrangement allows for flexible export.

The use of templates with the NetFlow version 9 export format provides several other key benefits:

• You can export almost any information from a router or switch, including Layer 2 through 7 information, routing information, IP version 6 (IPv6), IP version 4 (IPv4), multicast, and Multiprotocol Label Switching (MPLS) information. This new information allows new applications for export data and new views of network behavior.
• Third-party business partners who produce applications that provide NetFlow collector or display services for NetFlow are not required to recompile their applications each time a new NetFlow export field is added. Instead, they can use an external data file that documents the known template formats.
• New features can be added to NetFlow more quickly, without breaking current implementations.
• NetFlow is "future-proofed" against new or developing protocols, because the version 9 export format can be adapted to provide support for them and for other non-NetFlow-based approaches to data collection.

The NetFlow version 9 export packet header format is shown in the figure below.

The table below shows a typical example of exporting data using the NetFlow version 9 export format.

Figure 1

NetFlow Version 9 Export Format Packet Example

Additional information about the NetFlow export format version 9 and the export format architecture is available in the NetFlow version 9 Flow-Record Format document.

1.    enable

2.    configure terminal

3.    ipv6 unicast-routing

4.    mls flow {ip | ipv6} {destination | destination-source | full | interface-destination-source | interface-full | source}

5.    mls nde sender

6.    ip flow-export version 9

7.    ip flow-export destination {ip-address | hostname} udp-port

8.    interface type number

9.    ipv6 address ip-address/mask

Router# show mls nde

 NetFlow Data Export enabled 

 Exporting flows to 10.30.30.2 (12345)  172.16.10.2 (88)

 Exporting flows from 10.4.9.149 (58970)

 Version: 9

 Layer2 flow creation is disabled

 Layer2 flow export is disabled

 Include Filter not configured 

 Exclude Filter not configured 

 Total NetFlow Data Export Packets are:

    0 packets, 0 no packets, 0 records

 Total NetFlow Data Export Send Errors:

        IPWRITE_NO_FIB = 0

        IPWRITE_ADJ_FAILED = 0

        IPWRITE_PROCESS = 0

        IPWRITE_ENQUEUE_FAILED = 0

        IPWRITE_IPC_FAILED = 0

        IPWRITE_OUTPUT_FAILED = 0

        IPWRITE_MTU_FAILED = 0

        IPWRITE_ENCAPFIX_FAILED = 0

 NetFlow Aggregation Disabled