Company ABC has a 100Mbps fiber connection from headquarters to a remote office 200km (123 miles) away. This connection is provided by the local cable television company. ABC would like to extend a…

IS-IS is a link-state routing protocol operating at Layer 3 and has no capability to extend or transport customer Layer 2 VLAN frames across a provider network.

EIGRP is a Cisco proprietary distance-vector routing protocol that operates at Layer 3 and provides no mechanism for carrying customer Layer 2 VLAN traffic.

MPLS enables services such as VPLS and EoMPLS, which encapsulate customer Layer 2 frames - including 802.1q VLAN tags - inside MPLS label stacks for transport across the provider network. This decouples customer VLAN IDs from the provider's internal VLAN space, resolving the conflict that arises when both use overlapping 802.1q tags. The customer's VLAN is preserved end-to-end without the provider needing to retag or expose its internal topology.

802.1q is the standard the cable company already uses internally, which is precisely the source of the conflict - deploying more 802.1q would not resolve the VLAN ID collision between customer and provider domains.