Table Of Contents

NetFlow Export Datagram Formats

Versions 1, 5, 7 and 8

Version 9

NetFlow Export Datagram Formats

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NetFlow exports flow information in UDP datagrams in one of five formats:

•Version 1

•Version 5

•Version 7

•Version 8

•Version 9

Version 1 (V1) is the original format supported in the initial NetFlow releases. Version 5 (V5) is an enhancement that adds Border Gateway Protocol (BGP) autonomous system information and flow sequence numbers. Version 7 (V7) is an enhancement that exclusively supports NetFlow with Cisco Catalyst 5000 series switches equipped with a NetFlow feature card (NFFC). V7 is not compatible with Cisco routers. Version 8 (V8) is an enhancement that adds router-based aggregation schemes. Version 9 is an enhancement to support different technologies such as Multicast, Internet Protocol Security (IPSec), and Multi Protocol Label Switching (MPLS). Version 9 is not compatible with previous versions of CNS NetFlow Collection Engine.

Versions 2, 3, 4, and 6 either were not released or are not supported by CNS NetFlow Collection Engine.

This appendix describes these formats in the following sections:

–Versions 1, 5, 7 and 8

–Version 9

Versions 1, 5, 7 and 8

In Versions 1, 5, and 7, the datagram consists of a header and one or more flow records. The first field of the header contains the version number of the export datagram. Typically, a receiving application that accepts any of the format versions allocates a buffer large enough for the largest possible datagram from any of the format versions and then uses the header to determine how to interpret the datagram. The second field in the header contains the number of records in the datagram and should be used to search through the records.

All fields described in the format version tables are in network byte order.

•Table B-1 and Table B-2 describe the V1 header and flow record format, respectively

•Table B-3 and Table B-4 describe the V5 header and flow record format, respectively

•Table B-5 and Table B-6 describe the V7 header and flow record format, respectively

•Table B-7 describes the V8 header format

•Table B-8 describes the V8 RouterAS flow record format

•Table B-9 describes the V8 RouterProtoPort flow record

•Table B-10 describes the V8 RouterDstPrefix flow record

•Table B-11 describes the RouterSrcPrefix flow record

•Table B-12 describes the RouterPrefix flow record format

•Table B-13 describes the TosAS flow record format

•Table B-14 describes the TosProtoPort flow record format

•Table B-15 describes the PrePortProtocol flow record format

•Table B-16 describes the TosSrcPrefix flow record format

•Table B-17 describes the TosDstPrefix flow record format

•Table B-18 describes the TosPrefix flow record format

•Table B-19 describes the DestOnly flow record format

•Table B-20 describes the SrcDst flow record format

•Table B-21 describes the FullFlow flow record format.

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Note V8 data consists of header information that follows the same format as the other versions. However, the V8 flow record formats are separated based on the aggregation schemes that support router-based aggregation. Instead of one flow record table, you see five tables that describe the V8 flow record format for each individual aggregation scheme.

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We recommend that receiving applications perform a sanity check on datagrams to ensure that the datagrams are from a valid NetFlow source. You should first check the size of the datagram to verify that it is at least long enough to contain the version and count fields. You should next verify that the version is valid (1, 5, 7, or 8) and that the number of received bytes is enough for the header and count flow records (using the appropriate version).

Because NetFlow export uses UDP to send export datagrams, it is possible for datagrams to be lost. To determine whether flow export information has been lost, Version 5, Version 7, and

Version 8 headers contain a flow sequence number. The sequence number is equal to the sequence number of the previous datagram plus the number of flows in the previous datagram. After receiving a new datagram, the receiving application can subtract the expected sequence number from the sequence number in the header to derive the number of missed flows.

Datagram format Version 8 offers five router-based aggregation schemes allowing you to summarize CNS NetFlow Collection Engine export data on the router before the data is exported to the CNS NetFlow Collection Engine. The result is lower bandwidth requirements and reduced platform requirements for NetFlow data collection devices.

Router-based aggregation enables on-router aggregation by maintaining one or more extra NetFlow caches with different combinations of fields that determine which traditional flows are grouped together. These extra caches are called aggregation caches. As flows expire from the main flow cache, they are added to each enabled aggregation cache. The normal flow ager process runs on each active aggregation cache the same way it runs on the main cache. On-demand aging is also supported.

Table B-1 describes the V1 header format.

Table B-1 Version 1 Header Format 

Bytes	Contents	Description
0-1	version	NetFlow export format version number
2-3	count	Number of flows exported in this packet (1-24)
4-7	SysUptime	Current time in milliseconds since the export device booted
8-11	unix_secs	Current count of seconds since 0000 UTC 1970
12-16	unix_nsecs	Residual nanoseconds since 0000 UTC 1970

Table B-2 describes the V1 flow record format.

Table B-2 Version 1 Flow Record Format 

Bytes	Contents	Description
0-3	srcaddr	Source IP address
4-7	dstaddr	Destination IP address
8-11	nexthop	IP address of next hop router
12-13	input	SNMP index of input interface
14-15	output	SNMP index of output interface
16-19	dPkts	Packets in the flow
20-23	dOctets	Total number of Layer 3 bytes in the packets of the flow
24-27	First	SysUptime at start of flow
28-31	Last	SysUptime at the time the last packet of the flow was received
32-33	srcport	TCP/UDP source port number or equivalent
34-35	dstport	TCP/UDP destination port number or equivalent
36-37	pad1	Unused (zero) bytes
38	prot	IP protocol type (for example, TCP = 6; UDP = 17)
39	tos	IP type of service (ToS)
40	flags	Cumulative OR of TCP flags
41-43	pad1, pad2, pad3	Unused (zero) bytes
44-47	reserved	Unused (zero) bytes

Table B-3 describes the V5 header format.

Table B-3 Version 5 Header Format

Bytes	Contents	Description
0-1	version	NetFlow export format version number
2-3	count	Number of flows exported in this packet (1-30)
4-7	SysUptime	Current time in milliseconds since the export device booted
8-11	unix_secs	Current count of seconds since 0000 UTC 1970
12-15	unix_nsecs	Residual nanoseconds since 0000 UTC 1970
16-19	flow_sequence	Sequence counter of total flows seen
20	engine_type	Type of flow-switching engine
21	engine_id	Slot number of the flow-switching engine
22-23	sampling_interval	First two bits hold the sampling mode; remaining 14 bits hold value of sampling interval

Table B-4 describe the V5 flow record format.

Table B-4 Version 5 Flow Record Format 

Bytes	Contents	Description
0-3	srcaddr	Source IP address
4-7	dstaddr	Destination IP address
8-11	nexthop	IP address of next hop router
12-13	input	SNMP index of input interface
14-15	output	SNMP index of output interface
16-19	dPkts	Packets in the flow
20-23	dOctets	Total number of Layer 3 bytes in the packets of the flow
24-27	First	SysUptime at start of flow
28-31	Last	SysUptime at the time the last packet of the flow was received
32-33	srcport	TCP/UDP source port number or equivalent
34-35	dstport	TCP/UDP destination port number or equivalent
36	pad1	Unused (zero) bytes
37	tcp_flags	Cumulative OR of TCP flags
38	prot	IP protocol type (for example, TCP = 6; UDP = 17)
39	tos	IP type of service (ToS)
40-41	src_as	Autonomous system number of the source, either origin or peer
42-43	dst_as	Autonomous system number of the destination, either origin or peer
44	src_mask	Source address prefix mask bits
45	dst_mask	Destination address prefix mask bits
46-47	pad2	Unused (zero) bytes

Table B-5 and describes the V7 header format.

Table B-5 Version 7 (Catalyst 5000) Header Format

Bytes	Contents	Description
0-1	version	NetFlow export format version number
2-3	count	Number of flows exported in this flow frame (protocol data unit, or PDU)
4-7	SysUptime	Current time in milliseconds since the export device booted
8-11	unix_secs	Current seconds since 0000 UTC 1970
12-15	unix_nsecs	Residual nanoseconds since 0000 UTC 1970
16-19	flow_sequence	Sequence counter of total flows seen
20-23	reserved	Unused (zero) bytes

Table B-6 describe the V7 flow record format.

Table B-6 Version 7 (Catalyst 5000) Flow Record Format 

Bytes	Contents	Description
0-3	srcaddr	Source IP address; in case of destination-only flows, set to zero.
4-7	dstaddr	Destination IP address.
8-11	nexthop	Next hop router; always set to zero.
12-13	input	SNMP index of input interface; always set to zero.
14-15	output	SNMP index of output interface.
16-19	dPkts	Packets in the flow.
20-23	dOctets	Total number of Layer 3 bytes in the packets of the flow.
24-27	First	SysUptime, in milliseconds, at start of flow.
28-31	Last	SysUptime, in milliseconds, at the time the last packet of the flow was received.
32-33	srcport	TCP/UDP source port number; set to zero if flow mask is destination-only or source-destination.
34-35	dstport	TCP/UDP destination port number; set to zero if flow mask is destination-only or source-destination.
36	flags	Flags indicating, among other things, what flow fields are invalid.
37	tcp_flags	TCP flags; always set to zero.
38	prot	IP protocol type (for example, TCP = 6; UDP = 17); set to zero if flow mask is destination-only or source-destination.
39	tos	IP type of service; switch sets it to the ToS of the first packet of the flow.
40-41	src_as	Source autonomous system number, either origin or peer; always set to zero.
42-43	dst_as	Destination autonomous system number, either origin or peer; always set to zero.
44	src_mask	Source address prefix mask; always set to zero.
45	dst_mask	Destination address prefix mask; always set to zero.
46-47	flags	Flags indicating, among other things, what flows are invalid.
48-51	router_sc	IP address of the router that is bypassed by the Catalyst 5000 series switch. This is the same address the router uses when it sends NetFlow export packets. This IP address is propagated to all switches bypassing the router through the FCP protocol.

Table B-7 describes the V8 header format.

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Note Version 7 AS information is not supported in current implementations of the Catalyst 5000 series switch.

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Table B-7 Version 8 Header Format 

Bytes	Contents	Description
0-1	version	NetFlow export format version number
2-3	count	Number of flows exported in this flow frame (protocol data unit, or PDU)
4-7	SysUptime	Current time in milliseconds since the export device booted
8-11	unix_secs	Current seconds since 0000 UTC 1970
12-15	unix_nsecs	Residual nanoseconds since 0000 UTC 1970
16-19	flow_sequence	Sequence counter of total flows seen
20	engine_type	Type of flow switching engine
21	engine_id	ID number of the flow switching engine
22	aggregation	Aggregation method being used
23	agg_version	Version of the aggregation export
24-27	reserved	Unused (zero) bytes

Table B-8 describes the V8 RouterAS flow record format.

Table B-8 Version 8 RouterAS Flow Record Format 

Bytes	Contents	Description
0-3	flows	Number of flows
4-7	dPkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20-21	src_as	Source autonomous system number, either origin or peer; always set to zero
22-23	dst_as	Destination autonomous system number, either origin or peer; always set to zero
24-25	input	SNMP index of input interface; always set to zero
26-27	output	SNMP index of output interface

Table B-9 describes the V8 RouterProtoPort flow record.

Table B-9 Version 8 RouterProtoPort Flow Record Format 

Bytes	Contents	Description
0-3	flows	Number of flows
4-7	dPkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20	prot	IP protocol type (for example, TCP = 6; UDP = 17); set to zero if flow mask is destination-only or source-destination
21	pad	Unused (zero) bytes
22-23	reserved	Unused (zero) bytes
24-25	srcport	TCP/UDP source port number; set to zero if flow mask is destination-only or source-destination
26-27	dstport	TCP/UDP destination port number; set to zero if flow mask is destination-only or source-destination

Table B-10 describes the V8 RouterDstPrefix flow record.

Table B-10 Version 8 RouterDstPrefix Flow Record Format 

Bytes	Contents	Description
0-3	flows	Number of flows
4-7	dPkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20-23	dst_prefix	Destination IP address prefix
24	dst_mask	Destination address prefix mask; always set to zero
25	pad	Unused (zero) bytes
26-27	dst_as	Destination autonomous system number, either origin or peer; always set to zero
28-29	output	SNMP index of output interface
30-31	reserved	Unused (zero) bytes

Table B-11 describes the RouterSrcPrefix flow record.

Table B-11 Version 8 RouterSrcPrefix Flow Record Format 

Bytes	Contents	Description
0-3	flows	Number of flows
4-7	dPkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20-23	src_prefix	Source IP address prefix
24	src_mask	Source address prefix mask; always set to zero
25	pad	Unused (zero) bytes
26-27	src_as	Source autonomous system number, either origin or peer; always set to zero
28-29	input	SNMP index of input interface; always set to zero
30-31	reserved	Unused (zero) bytes

Table B-12 describes the RouterPrefix flow record format.

Table B-12 Version 8 RouterPrefix Flow Record Format 

Bytes	Contents	Description
0-3	flows	Number of flows
4-7	dPkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20-23	src_prefix	Source IP address prefix
24-27	dst_prefix	Destination IP address prefix
28	dst_mask	Source address prefix mask; always set to zero
29	src_mask	Destination address prefix mask; always set to zero
30-31	reserved	Unused (zero) bytes
32-33	src_as	Source autonomous system number, either origin or peer; always set to zero
34-35	dst_as	Destination autonomous system number, either origin or peer; always set to zero
36-37	input	SNMP index of input interface; always set to zero
38-39	output	SNMP index of output interface

Table B-13 describes the TosAS flow record format.

Table B-13 Version 8 TosAS Record Format 

Bytes	Contents	Description
0-3	flows	Number of flows
4-7	dPkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20-21	src_as	Source autonomous system number, either origin or peer; always set to zero
22-23	dst_as	Destination autonomous system number, either origin or peer; always set to zero
24-25	input	SNMP index of input interface; always set to zero
26-27	output	SNMP index of output interface
28	tos	Type of service
29	pad	Unused (zero) bytes
30-31	reserved	Unused (zero) bytes

Table B-14 describes the TosProtoPort flow record format.

Table B-14 Version 8 TosProtoPort Record Format 

Bytes	Contents	Description
0-3	flows	Number of flows
4-7	dPkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20	prot	IP protocol type (for example, TCP = 6; UDP = 17); set to zero if flow mask is destination-only or source-destination
21	Tos	IP Type of Service
22-23	reserved	Unused (zero) bytes
24-25	srcport	TCP/UDP source port number; set to zero if flow mask is destination-only or source-destination
26-27	dstport	TCP/UDP destination port number; set to zero if flow mask is destination-only or source-destination
28-29	input	SNMP index of input interface
30-31	output	SNMP index of output interface

Table B-15 describes the PrePortProtocol flow record format.

Table B-15 Version 8 PrePortProtocol Record Format 

Bytes	Contents	Description
0-3	flows	Number of flows
4-7	dpkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20-23	src_prefix	Source IP address prefix
24-27	dst_prefix	Destination IP address prefix
28	dst_mask	Destination address prefix mask
29	src_mask	Source address prefix mask
30	Tos	IP Type of Service
31	prot	IP protocol type (for example, TCP = 6; UDP = 17); set to zero if flow mask is destination-only or source-destination
32-33	srcport	TCP/UDP source port number; set to zero if flow mask is destination-only or source-destination
34-35	dstport	TCP/UDP destination port number; set to zero if flow mask is destination-only or source-destination
36-37	input	SNMP index of input interface
38-39	output	SNMP index of output interface

Table B-16 describes the TosSrcPrefix flow record format.

Table B-16 Version 8 TosSrcPrefix Record Format 

Bytes	Contents	Description
0-3	flows	Number of flows
4-7	dPkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20-23	src_prefix	Source IP address prefix
24	src_mask	Source address prefix mask
25	Tos	IP Type of Service
26-27	src_as	Source autonomous system number, either origin or peer
28-29	input	SNMP index of input interface
30-31	reserved	Reserved for future use

Table B-17 describes the TosDstPrefix flow record format.

Table B-17 Version 8 TosDstPrefix Record Format 

Bytes	Contents	Description
0-3	flows	Number of flows
4-7	dPkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20-23	dst_prefix	Destination IP address prefix
24	dst_mask	Destination address prefix mask
25	Tos	IP Type of Service
26-27	dst_as	Destination autonomous system number, either origin or peer
28-29	output	SNMP index of output interface
30-31	reserved	Unused (zero) bytes

Table B-18 describes the TosPrefix flow record format.

Table B-18 Version 8 TosPrefix Record Format 

Bytes	Contents	Description
0-3	flows	Number of flows
4-7	dPkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20-23	src_prefix	Source IP address prefix
24-27	dst_prefix	Destination IP address prefix
28	dst_mask	Destination address prefix mask
29	src_mask	Source address prefix mask
30	Tos	IP Type of Service
31	pad	Unused (zero) bytes
32-33	src_as	Source autonomous system number, either origin or peer
34-35	dst_as	Destination autonomous system number, either origin or peer
36-37	input	SNMP index of input interface
38-39	output	SNMP index of output interface

Table B-19 describes the DestOnly flow record format.

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Note This Flow statistic record is only used in Catalyst 6000 Series DestOnly aggregation.

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Table B-19 Version 8 DestOnly Record Format 

Bytes	Contents	Description
0-3	dstaddr	Destination IP address
4-7	dPkts	Packets in the flow
8-11	dOctets	Total number of Layer 3 bytes in the packets of the flow
12-15	First	SysUptime, in seconds, at start of flow
16-19	Last	SysUptime, in seconds, at the time the last packet of the flow was received
20-21	Output	SNMP index of output interface
22	Tos	IP Type of Service
23	marked_tos	Type of Service of the packets that exceeded the contract
24-27	extraPkts	Packets that exceed the contract
28-31	router_sc	IP address of the router that is bypassed by the Catalyst 5000 series switch. This is the same address the router uses when it sends NetFlow export packets. This IP address is propagated to all switches bypassing the router through the FCP protocol.

Table B-20 describes the SrcDst flow record format.

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Note This Flow statistic record is used in Catalyst 6000 Series only SrcDst aggregation.

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Table B-20 Version 8 SrcDst Record Format 

Bytes	Contents	Description
0-3	dstaddr	Destination IP address
4-7	srcaddr	Source IP address; in case of destination-only flows, set to zero
8-11	dPkts	Packets in the flow
12-15	dOctets	Total number of Layer 3 bytes in the packets of the flow
16-19	First	SysUptime, in seconds, at start of flow
20-23	Last	SysUptime, in seconds, at the time the last packet of the flow was received
24-25	Output	SNMP index of output interface
26-27	Input	SNMP index of input interface
28	Tos	IP Type of Service
29	marked_tos	Type of Service of the packets that exceeded the contract
30-31	reserved	Unused (zero) bytes
32-35	extraPkts	Packets that exceed the contract
36-39	router_sc	IP address of the router that is bypassed by the Catalyst 5000 series switch. This is the same address the router uses when it sends NetFlow export packets. This IP address is propagated to all switches bypassing the router through the FCP protocol.

Table B-21 describes the FullFlow flow record format.

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Note This Flow statistic record is used in Catalyst 6000 Series only FullFlow aggregation.

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Table B-21 Version 8 FullFlow Record Format 

Bytes	Contents	Description
0-3	dstaddr	Destination IP address
4-7	srcaddr	Source IP address; in case of destination-only flows, set to zero
8-9	dstport	TCP/UDP destination port number; set to zero if flow mask is destination-only or source-destination
10-11	srcport	TCP/UDP source port number; set to zero if flow mask is destination-only or source-destination
12-15	dPkts	Packets in the flow
16-19	dOctets	Total number of Layer 3 bytes in the packets of the flow
20-23	First	SysUptime, in seconds, at start of flow
24-27	Last	SysUptime, in seconds, at the time the last packet of the flow was received
28-29	Output	SNMP index of output interface
30-31	Input	SNMP index of input interface
32	Tos	IP Type of Service
33	prot	IP protocol type (for example, TCP = 6; UDP = 17); set to zero if flow mask is destination-only or source-destination
34	marked_tos	Type of Service of the packets that exceeded the contract
35	pad	Unused (zero) bytes
36-39	extraPkts	Packets that exceed the contract
40-43	router_sc	IP address of the router that is bypassed by the Catalyst 5000 series switch. This is the same address the router uses when it sends NetFlow export packets. This IP address is propagated to all switches bypassing the router through the FCP protocol.

Version 9

The distinguishing feature of the NetFlow Version 9 format is that it is template based. Templates provide an extensible design to the record format, a feature that should allow future enhancements to NetFlow services without requiring concurrent changes to the basic flow-record format.

This section includes the following:

•Table B-22 describes Version 9 export packet

•Table B-23 describes Version 9 header format

•Table B-24 describes Version 9 template FlowSet format

•Table B-25 describes Version 9 field types

•Table B-26 describes Version 9 data FlowSet format

•Table B-27 describes Version 9 option template format

Packet Layout

The NetFlow Version 9 record format consists of a packet header followed by at least one or more template or data FlowSets. A template FlowSet provides a description of the fields that will be present in future data FlowSets. These data FlowSets may occur later within the same export packet or in subsequent export packets.

Template and data FlowSets can be intermingled within a single export packet, as illustrated in Table B-22.

Table B-22 Version 9 Export Packet

Packet Header

Template FlowSet

Data FlowSet

Data FlowSet

..................

Template FlowSet

Data FlowSet

Packet Header Format

The format of the NetFlow Version 9 packet header remains relatively unchanged from that of previous versions. Table B-23 describes the Version 9 header format.

Table B-23 Version 9 Header Format 

Bytes	Field Name	Description
0-1	version	NetFlow export format version number; for Version 9 this value is 0x0009.
2-3	count	Number of flow sets exported in this packet, both template and data (1-30).
4-7	SysUptime	Current time in milliseconds since the export device booted.
8-11	unix_secs	Current count of seconds since 0000 UTC 1970.
12-15	package_sequence	Sequence counter of all export packets sent by the export device. Note: This is a change from the Version 5 and Version 8 headers, where this number represented "total flows."
16-19	source_id	A 32-bit value that is used to guarantee uniqueness for all flows exported from a particular device.

Template FlowSet Format

One of the key elements in the new Version 9 format is the template FlowSet. Templates greatly enhance the flexibility of the NetFlow record format, because they allow a NetFlow collector or display application to process NetFlow data without necessarily knowing the format of the data in advance. Templates are used to describe the type and length of individual fields within subsequent NetFlow data records that match a template ID.

Example B-1 Template FlowSet Format

Table B-24 describes the Version 9 Template FlowSet format.

Table B-24 Version 9 Template FlowSet Format 

Field Name	Description
FlowSet ID	Distinguishes template records from data records. A template record always has a FlowSet ID in the range of 0-255.
Length	Refers to the total length of this FlowSet. Because an individual template FlowSet may contain multiple template IDs, the length value should be used to determine the position of the next FlowSet record, which could be either a template or a data FlowSet. Length is expressed in type/length/value (TLV) format, meaning that the value includes the bytes used for the FlowSet ID and the length bytes themselves, as well as the combined lengths of all template records included in this FlowSet.
Template ID	As a router generates different template FlowSets to match the type of NetFlow data it will be exporting, each template is given a unique ID. This uniqueness is local to the router that generated the template ID. Templates that define data record formats begin numbering at 256, because 0-255 are reserved for FlowSet IDs.
Field Count	The number of fields in this template record. Because a template FlowSet may contain multiple template records, this field allows the parser to determine the end of the current template record and the start of the next.
Field Type	Numeric value that represents the type of the field. The possible values of the field type are vendor specific. Cisco supplied values are consistent across all platforms that support NetFlow Version 9. The currently defined field types are detailed in Table B-25.
Field Length	The length of the Field Type field, in bytes.

Note the following:

•Template IDs are consistent across a router reboot. Template IDs should change only if the configuration of NetFlow on the export device changes.

•Templates periodically expire if they are not refreshed. Templates can be refreshed in two ways. A template can be resent every N number of export packets. A template can also be sent on a timer, so that it is refreshed every N number of minutes. Both options are user configurable.

Table B-25 describes the Version 9 field types.

Table B-25 Version 9 Field Type Definitions 

Field Type	Value	Description
BYTES_32	1	Counter with length N x 8 bits for bytes associated with an IP Flow.
PKTS_32	2	Counter with length N x 8 bits for packets associated with an IP Flow.
FLOWS	3	Number of main cache flows that were aggregated.
PROT	4	IP protocol byte
TOS	5	Type of service byte
TCP_FLAGS	6	TCP flags (cumulative OR of TCP flags)
SRC_PORT	7	TCP/User Datagram Protocol (UDP) source port number (for example, File Transfer Protocol [FTP], Telnet, or equivalent)
IPSRCADDR	8	Source IPv4 address
SRC_MASK	9	Source route mask bits
INPUT_SNMP	10	Input interface index
DST_PORT	11	TCP/UDP destination port number (for example, FTP, Telnet, or equivalent)
IPDSTADDR	12	Destination IPv4 address
DST_MASK	13	Destination route mask bits
OUTPUT_SNMP	14	Output interface index
NEXT_HOP	15	IPv4 address of next-hop router
SRC_AS	16	Source Border Gateway Protocol (BGP) autonomous-system number
DST_AS	17	Destination BGP autonomous-system number
BGP_NEXT_HOP	18	Next-hop router in the BGP domain
MUL_DPKTS	19	Packet count for IP multicast
MUL_DOCKETS	20	Octet (byte) count for IP multicast
LAST_SWITCH	21	System uptime at which the last packet of this flow was switched
FIRST_SWITCH	22	System uptime at which the first packet of this flow was switched
PKTS_65	24	64-bit counter for packets associated with an IP flow
TOTAL_BYTES_EXP	40	Number of bytes exported by the Observation Domain
TOTAL_EXP_PKTS_SENT	41	Number of Packets exported by the Observation Domain
TOTAL_FLOWS_EXP	42	Number of Flows exported by the Observation Domain

Data FlowSet Format

The following is an example of the Data FlowSet format.

Example B-2 Data FlowSet Format

Table B-26 describes the Version 9 Data FlowSet format.

Table B-26 Version 9 Data FlowSet Format 

Field Name	Description
FlowSet ID = Template ID	A FlowSet ID precedes each group of records within a Version 9 data FlowSet. The FlowSet ID maps to a (previously received) template ID. The collector and display applications should use the FlowSet ID to map the appropriate type and length to any field values that follow.
Length	The length of the data FlowSet. Length is expressed in TLV format, meaning that the value includes the bytes used for the FlowSet ID and the length bytes themselves, as well as the combined lengths of any included data records.
Record N - Field N	The remainder of the Version 9 data FlowSet is a collection of field values. The type and length of the fields have been previously defined in the template record referenced by the FlowSet ID/template ID.
Padding	Should be inserted to align the end of the FlowSet on a 32 bit boundary. Pay attention that the Length field will include those padding bits.

When interpreting the NetFlow Version 9 data FlowSet format, note that the fields cannot be parsed without a corresponding template ID. If a data FlowSet that does not have an appropriate template ID is received, the record should be discarded.

Options Template Format

One additional record type is very important within the NetFlow Version 9 specification: an options template (and its corresponding options data record). Rather than supplying information about IP flows, options are used to supply "meta-data" about the NetFlow process itself. The format of the options template is detailed in Example B-3.

Example B-3 Options Template Format

Table B-27 describes the Version 9 options template format.

Table B-27 Version 9 Options Template Format 

Field Name	Description
FlowSet ID = 1	Used to distinguish template records from data records. A template record always has a FlowSet ID of 1. A data record always has a nonzero FlowSet ID which is greater than 255.
Length	The total length of this FlowSet. Because an individual template FlowSet may contain multiple template IDs, the length value should be used to determine the position of the next FlowSet record, which could be either a template or a data FlowSet. Length is expressed in TLV format, meaning that the value includes the bytes used for the FlowSet ID and the length bytes themselves, as well as the combined lengths of all template records included in this FlowSet.
Template ID	As a router generates different template FlowSets to match the type of NetFlow data it will be exporting, each template is given a unique ID. This uniqueness is local to the router that generated the template ID. The Template ID is greater than 255. Template IDs inferior to 255 are reserved.
Option Scope Length	The length in bytes of any scope fields contained in this options template (the use of scope is described below).
Options Length	The length (in bytes) of any Options field definitions contained in this options template.
Scope Field 1 Type	The relevant portion of the NetFlow process to which the options record refers. Currently defined values follow: •0x0001 System •0x0002 Interface •0x0003 Line Card •0x0004 NetFlow Cache •0x0005 Template For example, sampled NetFlow can be implemented on a per-interface basis, so if the options record were reporting on how sampling is configured, the scope for the report would be 0x0002 (interface).
Scope Field 1 Length	The length (in bytes) of the Scope field, as it would appear in an options record.
Option Field 1 Type	Represents the type of the field that appears in the options record. Possible values are detailed in Table B-25.
Option Field 1 Length	The length (in bytes) of the field, as it would appear in an options record.
Padding	Should be inserted to align the end of the FlowSet on a 32 bit boundary. Pay attention that the Length field will include those padding bits.