Layer 2 Circuit Configuration Element Missing

B

In the given configuration, a Layer 2 circuit is configured using the L2Circuit protocol to connect with a remote neighbor whose IP address is 2.2.2.2 on interface xe-0/0/1.0. However, one configuration element is missing to bring up the Layer 2 circuit, and we need to identify it.

A Layer 2 circuit is a point-to-point connection that emulates a physical wire between two switches or routers. In Junos, Layer 2 circuits can be established using various protocols such as LDP, L2TPv3, CCC, or VPLS. In this case, the Layer 2 circuit is configured using the CCC (circuit cross-connect) protocol, which encapsulates Ethernet frames in a PPP-like protocol.

To establish a Layer 2 circuit using CCC, we need to configure the following elements:

1. The local interface that will be used for the circuit, in this case, xe-0/0/1.0.
2. The remote neighbor's IP address with whom the circuit will be established, in this case, 2.2.2.2.
3. The virtual circuit ID (VCID), which is a unique identifier that identifies the circuit between the local and remote peers.
4. The encapsulation type to be used for the circuit, which is ethernet-ccc in this case.

In the given configuration, we have configured the local interface and the encapsulation type, but we have not configured the VCID, which is required to bring up the Layer 2 circuit. Therefore, option B, the virtual circuit ID, is the missing configuration element that needs to be added to establish the Layer 2 circuit.

The other options, such as route target, targeted LDP session, and MPLS LSP, are not directly related to establishing a Layer 2 circuit using CCC. Route targets are used for VPNs, targeted LDP sessions are used for targeted LDP signaling, and MPLS LSPs are used for MPLS label switching. Therefore, they are not the missing configuration element required to bring up the Layer 2 circuit.