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Example: Grouping Source and Destination Prefixes into a Forwarding Class

Requirements

No special configuration beyond device initialization is required before configuring this example.

Overview

This example uses three routing devices: a customer edge (CE) device, a provider edge (PE) device, and a provider core (P) device.

Figure 1 shows the sample network.

Figure 1: SCU and DCU Sample Network

Source class usage (SCU) counts packets sent to the customer edge by performing lookup on the IP source address and the IP destination address. SCU makes it possible to track traffic originating from specific prefixes on the provider core and destined for specific prefixes on the customer edge.

DCU counts packets from customers by performing a lookup of the IP destination address. DCU makes it possible to track traffic originating from the customer edge and destined for specific prefixes on the provider core router.

On Device PE’s fe-1/2/1 interface, facing the provider core (represented by Device P), SCU input is configured with the source-class-usage input statement to track traffic originating at Device P and destined to Device CE. On this same interface, the destination-class-usage input statement is configured to track traffic originating at Device CE destined to the provider core.

Unlike destination class usage (DCU), which only requires implementation on a single interface, accounting for SCU must be enabled on two interfaces: the inbound and outbound interfaces traversed by the source class. You must define explicitly the two interfaces on which SCU monitored traffic is expected to arrive and depart. This is because SCU performs two lookups in the routing table: a source address (SA) and a destination address (DA) lookup. In contrast, DCU only has a single destination address lookup.

On Device PE’s fe-1/2/0 interface, facing Device CE, SCU output is configured with the source-class-usage output statement.

To account for traffic destined to the customer, the policy called scu_class uses route filters to place traffic into the gold1, gold2, and gold3 classes.

To account for traffic destined to the provider, the policy called dcu_class uses route filters to place traffic into the silver1, silver2, and silver3 classes.

The policies are then applied to the forwarding table.

The example uses static routes to provide connectivity and loopback interface addresses for testing the operation.

CLI Quick Configuration shows the configuration for all of the devices in Figure 1.

The section Step-by-Step Procedure describes the steps on Device PE.

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

Step-by-Step Procedure

1. Create the router interfaces.

   [edit interfaces]user@PE# set fe-1/2/0 unit 0 family inet accounting source-class-usage outputuser@PE# set fe-1/2/0 unit 0 family inet address 10.0.0.2/30
   user@PE# set fe-1/2/1 unit 0 family inet accounting source-class-usage inputuser@PE# set fe-1/2/1 unit 0 family inet accounting destination-class-usageuser@PE# set fe-1/2/1 unit 0 family inet address 10.1.0.1/30
   user@PE# set lo0 unit 0 family inet address 192.168.0.2/32

2. Configure BGP.

   [edit protocols bgp group ext]user@PE# set type externaluser@PE# set export send-directuser@PE# set neighbor 10.0.0.1 peer-as 100user@PE# set neighbor 10.1.0.2 peer-as 300

3. Configure the DCU policy.

   [edit policy-options policy-statement dcu_class]user@PE# set term silver1 from route-filter 5.0.0.0/24 orlongeruser@PE# set term silver1 then destination-class silver1
   user@PE# set term silver2 from route-filter 6.0.0.0/24 orlongeruser@PE# set term silver2 then destination-class silver2
   user@PE# set term silver3 from route-filter 7.0.0.0/24 orlongeruser@PE# set term silver3 then destination-class silver3

4. Configure the SCU policy.

   [edit policy-options policy-statement scu_class]user@PE# set term gold1 from route-filter 2.0.0.0/24 orlongeruser@PE# set term gold1 then source-class gold1
   user@PE# set term gold2 from route-filter 3.0.0.0/24 orlongeruser@PE# set term gold2 then source-class gold2
   user@PE# set term gold3 from route-filter 4.0.0.0/24 orlongeruser@PE# set term gold3 then source-class gold3

5. Apply the policies to the forwarding table.

   [edit routing-options forwarding-table]user@PE# set export dcu_classuser@PE# set export scu_class

   Note: You can refer to the same routing policy one or more times in the same or different export statement.

6. (Optional) Configure a routing policy that advertises direct routes.
   [edit policy-options policy-statement send-direct term 1]user@PE# set from protocol directuser@PE# set then accept
7. Configure the autonomous system (AS) number.
   [edit routing-options]user@PE# set autonomous-system 200

Results

From configuration mode, confirm your configuration by issuing the show interfaces, show protocols, show policy-options, and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

If you are done configuring the device, enter commit from configuration mode.

Verification

Confirm that the configuration is working properly.

• Making Sure That the DCU Policy Is Working
• Making Sure That the SCU Policy Is Working

Making Sure That the DCU Policy Is Working

Purpose

Verify that traffic sent from the provider core into the customer network is causing the DCU policy counters to increment.

Action

1. From Device P, ping an address in the customer network.
   user@P> ping rapid count 10000000 6.0.0.1

   PING 6.0.0.1 (6.0.0.1): 56 data bytes
   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!...

2. On Device PE, check the interface statistics on the interface facing the provider core.
   user@PE> show interfaces statistics fe-1/2/1.0

     Logical interface fe-1/2/1.0 (Index 108) (SNMP ifIndex 546) 
       Flags: SNMP-Traps 0x4000 Encapsulation: ENET2
       Input packets : 251956
       Output packets: 251961
       Protocol inet, MTU: 1500
         Flags: Sendbcast-pkt-to-re, DCU, SCU-in
                                                  Packets                Bytes
         Destination class            (packet-per-second)    (bits-per-second)
   
                             silver1                 7460               626640
                                     (                  0) (                 0)
                             silver2                22440              2401416
                                     (                256) (            171963)
                             silver3                 9004               756336
                                     (                  0) (                 0)
         Addresses, Flags: Is-Preferred Is-Primary
           Destination: 10.1.0.0/30, Local: 10.1.0.1, Broadcast: 10.1.0.3
   

Meaning

Packet and bit rates are displayed with packet and byte counters.

Alternatively, you can use the show interfaces destination-class all command to display the same information.

Making Sure That the SCU Policy Is Working

Purpose

Verify that traffic sent from the customer network into the provider core is causing the SCU policy counters to increment.

Action

1. From Device CE, ping an address in the customer network.
   user@CE> ping rapid count 10000000 2.0.0.1

   PING 6.0.0.1 (6.0.0.1): 56 data bytes
   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!...

2. On Device PE, check the interface statistics on the interface facing the customer network.
   user@PE> show interfaces statistics fe-1/2/0.0

     Logical interface fe-1/2/0.0 (Index 93) (SNMP ifIndex 554) 
       Flags: SNMP-Traps 0x4000 Encapsulation: ENET2
       Input packets : 32246
       Output packets: 32245
       Protocol inet, MTU: 1500
         Flags: Sendbcast-pkt-to-re, Is-Primary, SCU-out
                                                  Packets                Bytes
         Source class                 (packet-per-second)    (bits-per-second)
   
                               gold1                 8871               745164
                                     (                259) (            174497)
                               gold2                 1812               152208
                                     (                  0) (                 0)
                               gold3                 5711               479724
                                     (                  0) (                 0)
         Addresses, Flags: Is-Preferred Is-Primary
           Destination: 10.0.0.0/30, Local: 10.0.0.2, Broadcast: 10.0.0.3
   

Meaning

Packet and bit rates are displayed with packet and byte counters.

Alternatively, you can use the show interfaces source-class all command to display the same information.