SCU can be implemented over regular interfaces; it is also used in combination with Layer 3 VPNs. When you view SCU traffic on an ingress PE router, use the standard procedure outlined in Configuring SCU. However, when you enable packet counting for Layer 3 VPNs at the egress point of the MPLS tunnel, you need to take some additional steps.
To configure SCU on the egress router in a Layer 3 VPN, you must configure SCU on the the egress PE router and map the SCU-enabled input interface of that router to the VRF instance. This section contains these configuration procedures, an example, and commands you can issue to verify your work:
SCU over Layer 3 VPNs is not supported when the VRF table label is configured. Also, SCU is not supported over Layer 2 VPNs.
To enable SCU in a Layer 3 VPN, configure source class usage on the virtual loopback tunnel (vt) interface of the egress provider edge (PE) router that is either configured for or equipped with a Tunnel PIC. The interface is equivalent to the inbound SCU interface, so use the input statement at the [edit interfaces vt-interface-number unit 0 family inet accounting source-class-usage] hierarchy level:
- [edit]
- interfaces {
-
- vt-0/3/0 {
-
- unit 0 {
-
- family inet {
-
- accounting {
-
- source-class-usage {
- input;
- }
- }
- }
- }
- }
- }
Next, include the VPN loopback tunnel interface in the desired VRF instance at the [edit routing-instances routing-instance-name] hierarchy level:
- [edit]
- routing-instances {
-
- routing-instance-name {
- instance-type vrf;
- interface at-2/1/1.0;
- interface vt-0/3/0.0;
- route-distinguisher 10.250.14.225:100;
- vrf-import import-policy-name;
- vrf-export export-policy-name;
-
- protocols {
-
- bgp {
-
- group to-r4 {
- local-address 10.20.253.1;
- peer-as 400;
- neighbor 10.20.253.2;
- }
- }
- }
- }
- }
Since VPN traffic enters the egress router through the VPN loopback tunnel interface, you still need to determine the exit interface for this traffic. To complete your SCU configuration, configure the output version of source class usage on the exit interface of your egress router:
- [edit interfaces]
- at-1/1/0 {
-
- unit 0 {
-
- family inet {
-
- accounting {
-
- source-class-usage {
- output;
- }
- }
- }
- }
- }
