This article explains a simple method to verify data plane of an Eline (L2circuit/L2vpn). Generally, when we verify data plane of an Eline, we need people and traffic generators at both ends of the circuit. This article explains a simple method by which we can test the data plane of circuit just by having a single traffic generator at one end of the circuit.
Topology
In this solution, we are enabling a soft loop feature on one of the unused interfaces of PE2 so that traffic generated and forwarded by CPE1 will get replayed back by PE2 towards CPE1.
In the above topology, PE2 and CPE2 are connected using et-1/1/1.1250. I have multiple other services (FIA, Residential and Business customer. et..) running on different vlans of et-1/1/1. To avoid disruption to other services running on et-1/1/1, I used another unused (down) interface et-1/0/2 for testing the data plane.
I ran necessary commit changes to move circuit temporary to et-1/0/2 and brought the interface "up" by adding "gigether-options loopback" configuration knob. Config change snippet below
labroot@jtac-mx240-r2020-re0# show | compare
[edit logical-systems MX1_LS3 interfaces]
+ et-1/0/2 {
+ unit 1250 {
+ encapsulation vlan-ccc;
+ vlan-id 1250;
+ }
[edit logical-systems MX1_LS3 protocols l2circuit neighbor 2.2.2.1]
+ interface et-1/0/2.1250 {
+ virtual-circuit-id 1250;
- interface et-1/1/1.1250 {
- virtual-circuit-id 1250;
- }
[edit interfaces]
+ flexible-vlan-tagging;
+ encapsulation flexible-ethernet-services;
+ gigether-options {
+ loopback;
After the above changes, monitoring traffic stats on PE router interfaces will help us to confirm if the data plane looks good or not. In the below output, we can see that the traffic send by Traffic generator reached PE2 and PE2 is replaying it back towards PE1-CPE1
labroot@jtac-mx240-r2020-re0> show interfaces et-1/0/2
Physical interface: et-1/0/2, Enabled, Physical link is Up
Interface index: 157, SNMP ifIndex: 752
Link-level type: Flexible-Ethernet, MTU: 1522, MRU: 1530, Speed: 40Gbps, BPDU Error: None, Loop Detect PDU Error: None, Ethernet-Switching Error: None,
Loopback: Enabled (local), Source filtering: Disabled, Flow control: Enabled
...
##PE2
Interface: et-1/0/2.1250, Enabled, Link is Up
Flags: SNMP-Traps 0x4000
Encapsulation: VLAN-CCC
VLAN-Tag [ 0x8100.1250 ]
Local statistics: Current delta
Input bytes: 0 [0]
Output bytes: 0 [0]
Input packets: 0 [0]
Output packets: 0 [0]
Remote statistics:
Input bytes: 1734 (808 bps) [1734]
Output bytes: 1734 (808 bps) [1734]
Input packets: 17 (1 pps) [17]
Output packets: 17 (1 pps) [17]
Traffic statistics:
Input bytes: 1734 [1734]
Output bytes: 1734 [1734]
Input packets: 17 [17]
Output packets: 17 [17]
##PE1
Interface: et-1/1/3.1250, Enabled, Link is Up
Input bytes: 1692 (808 bps) [204]
Output bytes: 1692 (808 bps) [204]
Input packets: 17 (1 pps) [2]
Output packets: 17 (1 pps) [2]
Input bytes: 1692 [204]
Output bytes: 1692 [204]
Input packets: 17 [2]
Output packets: 17 [2]