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Example: Sampling and Discard Accounting Configuration

Discard accounting allows you to sample traffic, send it to a flow server for analysis, and discard all packets without forwarding them to their intended destination. Discard accounting is enabled with the discard accounting group-name statement in a firewall filter at the [edit firewall family inet filter filter-name term term-name then] hierarchy level. Then, the filter is applied to an interface with the filter statement at the [edit interfaces interface-name unit unit-number family inet] hierarchy level and processed with the output statement at the [edit forwarding-options accounting group-name] hierarchy level.

Figure 29: Active Flow Monitoring—Sampling and Discard Accounting Topology Diagram

Image g003105.gif

In Figure 29, traffic from Router 1 arrives on the monitoring router’s Gigabit Ethernet ge-2/3/0 interface. The export interface leading to the flow server is fe-1/0/0 and there is no exit interface.

In this example, TCP traffic is sent to one accounting group and all other traffic is diverted to a second group. After being sampled and counted, the two types of traffic are acted upon by the sampling and accounting processes. These processes create flow records and send the records to the version 8 flow server for analysis. Because multiple types of traffic are sent to the same server, we recommend that you configure the engine-id, engine-type, and source-address statements manually in your accounting and sampling hierarchies. This way, you can differentiate between traffic types when they arrive at the flow server.



[edit]
interfaces {


sp-2/0/0 { # This adaptive services interface creates the
flow records.


unit 0 {


family inet {


address 10.5.5.1/32 {
destination 10.5.5.2;
}


}


}


}




               
fe-1/0/0 { #
This is the interface where records are sent to the flow server.


unit 0 {


family inet {
address 10.60.2.2/30;
}


}


}




               
ge-2/3/0 { #
This is the input interface where traffic enters the router.


unit 0 {


family inet {


filter {
input catch_all;
}


address 10.1.1.1/20;
}


}


}


}
forwarding-options {


               
sampling { #
The router samples the traffic.


input {


family inet {
                   
rate 100; # One out of every 100 packets is sampled.
}


}




                 
output { #
The sampling process creates and exports flow records.


                   
flow-server 10.60.2.1 { # You can configure a variety of settings.
port 2055;
version 8;


                     
aggregation { # Aggregation is unique to flow version 8.
protocol-port;
source-destination-prefix;
}


}


aggregate-export-interval 90;
flow-inactive-timeout 60;
flow-active-timeout 60;


                   
interface sp-2/0/0 { # This statement enables PIC-based sampling.
engine-id 5; # Engine statements are dynamic, but can be
configured.
engine-type 55;
                   
source-address 10.60.2.2; # You must configure this statement.
}


}


}




               
accounting counter1 { # This discard accounting process handles default traffic.


                 
output { #
This process creates and exports flow records.
flow-inactive-timeout 65;
flow-active-timeout 65;


                   
flow-server 10.60.2.1 { # You can configure a variety of settings.
port 2055;
version 8;


                     
aggregation { # Aggregation is unique to version 8.
protocol-port;
source-destination-prefix;
}


}




                   
interface sp-2/0/0 {  # This statement enables PIC-based discard accounting.
engine-id 1; # Engine statements are dynamic, but can be
configured.
engine-type 11;
                   
source-address 10.60.2.3; # You must configure this statement.
}


}


}




               
accounting t2 { # The second discard accounting process handles the TCP traffic.


                 
output { #
This process creates and exports flow records.
aggregate-export-interval 90;
flow-inactive-timeout 65;
flow-active-timeout 65;


                   
flow-server 10.60.2.1 {                   # You can configure
a variety of settings for the server.
port 2055;
version 8;


                     
aggregation { # Aggregation is unique to version 8.
protocol-port;
source-destination-prefix;
}


}




                   
interface sp-2/0/0 { # This statement enables PIC-based discard accounting.
engine-id 2; # Engine statements are dynamic, but can be
configured.
engine-type 22;
                   
source-address 10.60.2.4;# You must configure this statement.
}


}


}


}
firewall {


family inet {


                 
filter catch_all { # Apply the firewall filter on the input interface.


                   
term t2 { # This places TCP traffic into one group for sampling and


from { # discard accounting.
protocol tcp;
}




then {
                     
count c2;# The count action counts traffic as it
enters the router.
                     
sample; # The sample action sends the traffic
to the sampling process.
                     
discard accounting t2; # The discard accounting discards traffic.
}


}




                   
term default { # Performs sampling and discard accounting on all other traffic.


then {
                     
count counter; # The count action counts traffic as
it enters the router.
                     
sample#
The sample action sends the traffic to
the sampling process.
                     
discard accounting counter1; # This activates discard accounting.
}


}


}


}


}

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