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Configuring Inline Sampling

On MX Series routers only, you can configure active sampling to be performed on an inline data path without the need for a services Dense Port Concentrator (DPC). To do this, you define a sampling instance with specific properties. One Flexible PIC Concentrator (FPC) can support only one instance; for each instance, either services PIC-based sampling or inline sampling is supported per family. As a result, a particular instance can define PIC-based sampling for one family and inline sampling for a different family. Both IPv4 and IPv6 are supported for inline sampling.

Inline sampling supports a specified sampling output format designated IP_FIX. It uses UDP as the transport protocol.

Before you configure inline sampling, you should ensure that you have adequately sized hash tables for IPv4 and IPv6 flow sampling. These tables can use 1 to 15 256k areas, and each is assigned a default value of one such area. When anticipated traffic volume requires larger tables, allocate larger tables.

1. Go to the flow-table-size hierarchy level for inline services on the FPC that processes the monitored flows.
   [edit]user@host# edit chassis fpc 0 inline-services flow-table-size
2. Specify the required sizes for the sampling hash tables.
   [edit chassis fpc 0 inline-services flow-table-size]user@host# set ipv4-flow-table-size 5user@host# set ipv6-flow-table-size 5

   Note: When you set the flow hash table sizes, remember: Any change in the configured size of flow hash table sizes initiates an automatic reboot of the FPC. The total number of units used for both IPv4 and IPv6 cannot exceed 15.

The configuration for inline sampling on MX80 routers is slightly different.

1. Enable inline sampling and specify the source address for the traffic.
   [edit forwarding-options sampling instance instance-name family inet output]user@host# set inline-jflow source address address
2. Specify the IP_FIX output format.
   [edit forwarding-options sampling instance instance-name family inet output flow-server address]user@host# set version-ipfix template ipv4
3. Specify the output properties.
   [edit services flow-monitoring]user@host# set version-ipfix

   The output format properties are common to other output formats and are described in “Configuring Flow Aggregation to Use IPFIX Flow Templates”.

The following is an example of the sampling configuration for an instance that supports inline sampling on family inet and PIC-based sampling on family inet6:

The following example shows the output format configuration:

• Sampling run-length and clip-size are not supported.
• For inline configurations, each family can support only one collector.

Note: Inline sampling instances can handle only up to 65536 AS paths. If the total number of AS paths exceed the maximum limit, the AS paths that have AS index greater than 65536 are discarded and counted as error. Flow records associated with such AS paths show the AS value as 0xFFFFFFFF . However, this limitation does not impact normal fowarding operations.