1. A system comprising: an access node, having an access node processor coupled to an access node data storage device having stored therein software instructions that, when executed by the access node processor, cause the access node processor to perform operations including: executing a routing protocol on the access node to establish adjacency with a core network node in an access mode; mapping an access network Layer 2 service identifier to a core network service identifier, wherein the mapping includes mapping of a VLAN to an ISID; advertising the mapping for an L2VPN service to the core network node; and sending network traffic from the access node to the core network node without encapsulation; and wherein the core network node includes a core network node processor coupled to a core network node data storage device having stored therein software instructions that, when executed by the core network node processor, cause the core network node processor to perform operations including: executing, using one or more processors, a routing protocol from the core network node towards the access node in an access mode; extracting, using the one or more processors, an access network Layer 2 service identifier to a core network service identifier mapping from a routing protocol message received from the access node, wherein the access network Layer 2 service identifier to a core network service identifier mapping includes mapping of a VLAN to an ISID; creating, using the one or more processors, a VLAN on the core network node and adding to the VLAN a port corresponding to a port on which the service mapping was received; and preventing, using the one or more processors, routing messages received from other core network nodes from reaching the access node.