The L2 NID based architecture for vCPE/NFV deployments faces several challenges:
1) It can cause MAC address scale issues in the NFV data center switching infrastructure as thousands of customer MAC addresses may need to be learned.
2) It extends customer layer 2 domains to the NFV data center, increasing security risks from misconfigured customer networks.
3) There is a potential risk of layer 2 loops occurring between customer networks and the service provider infrastructure without proper demarcation and loop prevention.
4) Achieving high availability between redundant vCPE instances requires reliable tracking of the connectivity between the L2 NID and vCPE, which adds complexity.