Before using CEN, read the limits first.

Resource Default limit Exception
The number of CEN instances per account 5 Submit a ticket
The number of attached networks per region 5 Submit a ticket
The number of bandwidth packages in the same interconnection area per account 1 No exception
The number of contained regions per CEN instance 5 Submit a ticket
Limits on VPC with ClassicLink enabled The VPC cannot use the IP address range 10.0.0.0/8. No exception
Networks You cannot attach VPCs or VBRs that are using Express Connect to a CEN instance. No exception
The number of route entries in a CEN instance 100  Submit a ticket