Cisco Cisco IOS Software Release 12.2(27)SBC
MPLS-Aware NetFlow
Information About MPLS-Aware NetFlow
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Cisco IOS Release: Multiple releases (see Feature Information table)
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MPLS Flows
MPLS-Aware NetFlow collects statistics on a per-flow basis just as NetFlow does. A flow is a
unidirectional set of packets (IP or MPLS) that arrive at the router on the same subinterface, and have
the same source and destination IP addresses, the same Layer 4 protocol, the same TCP and UDP source
and destination ports, and the same type of service (ToS) byte in the IP header.
unidirectional set of packets (IP or MPLS) that arrive at the router on the same subinterface, and have
the same source and destination IP addresses, the same Layer 4 protocol, the same TCP and UDP source
and destination ports, and the same type of service (ToS) byte in the IP header.
An MPLS flow contains up to three of the same incoming MPLS labels of interest with experimental bits
and end-of-stack bits in the same positions in the packet label stack. MPLS-Aware NetFlow captures
MPLS traffic that contains both IP and non-IP packets. It reports non-IP packets, but sets the IP NetFlow
fields to 0. It can also be configured to capture and report IP packets, setting to 0 the IP NetFlow fields.
MPLS-Aware NetFlow uses the NetFlow Version 9 export format. MPLS-Aware NetFlow exports up to
three labels of interest from the incoming label stack and traditional NetFlow data.
and end-of-stack bits in the same positions in the packet label stack. MPLS-Aware NetFlow captures
MPLS traffic that contains both IP and non-IP packets. It reports non-IP packets, but sets the IP NetFlow
fields to 0. It can also be configured to capture and report IP packets, setting to 0 the IP NetFlow fields.
MPLS-Aware NetFlow uses the NetFlow Version 9 export format. MPLS-Aware NetFlow exports up to
three labels of interest from the incoming label stack and traditional NetFlow data.
MPLS Label Stack
As packets move through an MPLS network, LSRs can add labels to the MPLS label stack. The label is
a short, four-byte, fixed-length, locally-significant identifier that is used to identify a Forwarding
Equivalence Class (FEC). The label that is put on a particular packet represents the FEC to which that
packet is assigned. LSRs in an MPLS cloud can add up to six labels to the MPLS label stack. An LSR
adds the MPLS labels to the top of the IP packet.
a short, four-byte, fixed-length, locally-significant identifier that is used to identify a Forwarding
Equivalence Class (FEC). The label that is put on a particular packet represents the FEC to which that
packet is assigned. LSRs in an MPLS cloud can add up to six labels to the MPLS label stack. An LSR
adds the MPLS labels to the top of the IP packet.
shows an example of an incoming MPLS label
stack that LSRs added to an IP packet as it traversed an MPLS cloud. The label type is the MPLS
technology that allocated the label; for example, Label Distribution Protocol (LDP) allocated label 33,
and the Carrier Supporting Carrier (CSC) technology allocated label 42.
technology that allocated the label; for example, Label Distribution Protocol (LDP) allocated label 33,
and the Carrier Supporting Carrier (CSC) technology allocated label 42.
Figure 1
Example of an MPLS Label Stack Added to an IP Packet in an MPLS Cloud
In the example of an MPLS label stack in
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The 33 represents the top label of this packet.
This label was the last label added to the MPLS label stack and the label that MPLS-Aware NetFlow
captures if you indicate the label of interest as 1.
captures if you indicate the label of interest as 1.
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The 42 represents the second label in the MPLS stack.
88306
33
42
IP packet
MPLS labels
Miscellaneous bits
Top-level label
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Lb4–Lb6 B IP Header
Data
B
B
B
Label Label type Location
in stack
33
LDP
1 (top)
42
CSC
2
16
VPN
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