Network and Resource Planning

Plan the network and required resources before, during, and after the migration.

Network Planning: Plan CIDR blocks of VPCs and their subnets, and route tables of VPCs and the enterprise router.
Resource Planning: Plan the quantity, names, and other parameters of cloud resources, including VPCs, ECSs, and the enterprise router.

Network Planning

During the migration, in addition to routes for communications among enterprise router and VPCs, you also need to add routes for verification and temporary communications. After the migration is complete, you can delete unnecessary routes. For details about the network planning, see Table 1.

The following figures show the network in different phases.

Figure 1
Figure 2
Figure 3

The routes in the figures are only examples for your reference. You need to plan routes based on service requirements.

Figure 1 Networking topology before migration

Figure 2 Networking topology during migration

Figure 3 Networking topology after migration

**Table 1** Network planning details
Route Table	Description
VPC route table	Table 2 lists the routes in this route table. Before the migration, the destination of the route with next hop set to VPC peering connection is a CIDR block of a VPC subnet. This only connects specific subnets of VPCs. During the migration, add routes as follows: The routes for temporary communications ensure that traffic is not interrupted when original routes added for VPC peering connections are deleted. The next hop of the routes can be any VPC peering connection of the VPC. The route destinations cannot be used by any other services. You can set the destinations to those that are rarely used. In this example, the destinations are 1.1.1.1/32, 1.1.1.2/32, and 1.1.1.3/32. The routes are used for communications between the enterprise router and VPCs, with the destination set to a large CIDR block and next hop to the enterprise router. The route destination must include the CIDR blocks of all VPCs that need to communicate with each other and cannot be used by any other services. In this example, the destination is 172.16.0.0/14, which includes the CIDR blocks of three VPCs, 172.16.0.0/16, 172.17.0.0/16, and 172.18.0.0/16. Routes with the next hop set to the enterprise router are used for communications between the VPCs and enterprise router. The route destinations cannot be the CIDR blocks configured for VPC peering connections and are not used to allow communications through VPC peering connections. In this example, the destinations are 172.16.253.0/29, 172.17.253.0/29, and 172.18.253.0/29. NOTICE: The routes for temporary communications are necessary to ensure that traffic is not interrupted when original routes added for VPC peering connections are deleted. If you use the migration solution provided in this practice, traffic will not be interrupted. However, if traffic is interrupted in the migration process, contact customer service to evaluate your migration solution. The large CIDR block must include the CIDR blocks of all VPCs that need to communicate with each other. If one large CIDR block cannot include the CIDR blocks of all VPCs, you can configure more large CIDR blocks. After the migration, delete the routes for verification and temporary communications. NOTICE: After the migration, you can continue to use the routes with the destination set to the large CIDR block. You can also add routes with destinations that are the same as those of the original routes and then delete the routes with the destination set to the large CIDR block.
Enterprise router route table	Table 3 lists the routes in this route table. During the migration, add routes that with destinations set to VPC CIDR blocks to allow communications among the enterprise router and VPCs. If Default Route Table Association and Default Route Table Propagation are enabled for the enterprise router, routes with destinations set to VPC CIDR blocks are automatically added when you attach the VPCs to the enterprise router. CAUTION: If the CIDR blocks of VPCs connected by a VPC peering connection overlap, do not enable Default Route Table Propagation for the enterprise router. This function adds routes with entire VPC CIDR blocks as destinations. If VPC CIDR blocks overlap, there will be route conflicts. In this case, you need to manually add routes with next hop set to VPC attachment to the route table of the enterprise router.

**Table 2** VPC route table details
VPC	VPC Route Table	Destination	Next Hop Type	Next Hop	Route Type	Route Function	Phase
VPC-A	rtb-vpc-A	172.17.0.0/24	VPC peering connection	peer-AB	Custom	Destination: subnet-B01 in VPC-B Connects subnet-A01 to subnet-B01	Before/During migration
		172.18.0.0/24	VPC peering connection	peer-AC	Custom	Destination: subnet-C01 in VPC-C Connects subnet-A01 to subnet-C01	Before/During migration
		1.1.1.1/32	VPC peering connection	peer-AB	Custom	Destination: Any IP address that is not used by other services Ensures that traffic flowing through VPC peering connections is not interrupted during the migration.	During migration
		172.16.0.0/14	Enterprise router	er-ABC	Custom	Destination: A large CIDR block that can include the CIDR blocks of the three VPCs Connects VPC-A to er-ABC	During/After migration
		172.17.253.0/29	Enterprise router	er-ABC	Custom	Destination: subnet-B02 in VPC-B Connects subnet-B02 to er-ABC	During migration
		172.18.253.0/29	Enterprise router	er-ABC	Custom	Destination: subnet-C02 in VPC-C Connects subnet-C02 to er-ABC	During migration
VPC-B	rtb-vpc-B	172.16.0.0/24	VPC peering connection	peer-AB	Custom	Destination: subnet-A01 in VPC-A Connects subnet-A01 to subnet-B01	Before/During migration
		172.18.0.0/24	VPC peering connection	peer-BC	Custom	Destination: subnet-C01 in VPC-C Connects subnet-B01 to subnet-C01	Before/During migration
		1.1.1.2/32	VPC peering connection	peer-AB	Custom	Destination: Any IP address that is not used by other services Ensures that traffic flowing through VPC peering connections is not interrupted during the migration.	During migration
		172.16.0.0/14	Enterprise router	er-ABC	Custom	Destination: A large CIDR block that can include the CIDR blocks of the three VPCs Connects VPC-B to er-ABC	During/After migration
		172.16.253.0/29	Enterprise router	er-ABC	Custom	Destination: subnet-A02 in VPC-A Connects subnet-A02 to er-ABC	During migration
		172.18.253.0/29	Enterprise router	er-ABC	Custom	Destination: subnet-C02 in VPC-C Connects subnet-C02 to er-ABC	During migration
VPC-C	rtb-vpc-C	172.16.0.0/24	VPC peering connection	peer-AC	Custom	Destination: subnet-A01 in VPC-A Connects subnet-A01 to subnet-C01	Before/During migration
		172.17.0.0/24	VPC peering connection	peer-BC	Custom	Destination: subnet-B01 in VPC-B Connects subnet-B01 to subnet-C01	Before/During migration
		1.1.1.3/32	VPC peering connection	peer-AC	Custom	Destination: Any IP address that is not used by other services Ensures that traffic flowing through VPC peering connections is not interrupted during the migration.	During migration
		172.16.0.0/14	Enterprise router	er-ABC	Custom	Destination: A large CIDR block that can include CIDR blocks of the three VPCs Connects VPC-C to er-ABC	During/After migration
		172.16.253.0/29	Enterprise router	er-ABC	Custom	Destination: subnet-A02 in VPC-A Connects subnet-A02 to er-ABC	During migration
		172.17.253.0/29	Enterprise router	er-ABC	Custom	Destination: subnet-B02 in VPC-B Connects subnet-B02 to er-ABC	During migration

**Table 3** Details of the enterprise router route table
Enterprise Router	Route Table	Destination	Next Hop	Attached Resource	Route Type	Route Function	Phase
er-ABC	defaultRouteTable	172.16.0.0/16	er-attach-A	VPC-A	Propagated	Destination: VPC-A Connects VPC-A to er-ABC	During/After migration
		172.17.0.0/16	er-attach-B	VPC-B	Propagated	Destination: VPC-B Connects VPC-B to er-ABC	During/After migration
		172.18.0.0/16	er-attach-C	VPC-C	Propagated	Destination: VPC-C Connects VPC-C to er-ABC	During/After migration

Resource Planning

Table 4 lists the enterprise router and also resources that are temporarily required and can be deleted after the migration.

The following resource planning details are only examples for your reference. You need to plan resources based on service requirements.

**Table 4** Resource planning for replacing VPC peering connections with an enterprise router
Resource	Description
VPC	Table 5 shows details about the required VPCs. Before the migration, there are three VPCs. Each VPC has a subnet that is associated with the default VPC route table. During the migration, create one more subnet that is not used by any services in each VPC. These subnets cannot communicate with each other through VPC peering connections and are used for communications between the VPCs and enterprise router. After the migration, delete the subnets that are used for verifying communications.
VPC peering connection	Table 6 shows details about the required VPC peering connections. After the migration, delete the VPC peering connections.
ECS	Table 7 shows details about the required ECSs. Before the migration, there are three ECSs that are running services. During the migration, create one more ECS in each verification subnet for communications between the VPCs and enterprise router. After the migration, delete the ECSs in verification subnets.
Enterprise router	The enterprise router and the VPC peering connections are in the same region. Table 8 shows details about the enterprise router. During the migration, create an enterprise router and three VPC attachments. Table 9 shows details about the VPC attachments. Enable Default Route Table Association and Default Route Table Propagation when you create the enterprise router to automatically add routes. CAUTION: If the CIDR blocks of VPCs connected by a VPC peering connection overlap, do not enable Default Route Table Propagation for the enterprise router. This function adds routes with entire VPC CIDR blocks as destinations. If VPC CIDR blocks overlap, there will be route conflicts. In this case, you need to manually add routes with next hop set to VPC attachment to the route table of the enterprise router. Do not enable Auto Add Routes when you create the three VPC attachments. If this option is enabled, Enterprise Router automatically adds routes (with this enterprise router as the next hop and 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 as the destinations) to all route tables of the VPC. During the migration, manually add routes with destinations set to the large CIDR block in the VPC route tables.

**Table 5** VPC details
VPC	VPC CIDR Block	Subnet	Subnet CIDR Block	Association Route Table	Subnet Is Used to	Phase
VPC-A	172.16.0.0/16	subnet-A01	172.16.0.0/24	Default route table	Deploy services.	During/After migration
VPC-A	172.16.0.0/16	subnet-A02	172.16.253.0/29	Default route table	Verify the communications between the VPC and the enterprise router.	During migration
VPC-B	172.17.0.0/16	subnet-B01	172.17.0.0/24	Default route table	Deploy services.	During/After migration
VPC-B	172.17.0.0/16	subnet-B02	172.17.253.0/29	Default route table	Verify the communications between the VPC and the enterprise router.	During migration
VPC-C	172.18.0.0/16	subnet-C01	172.18.0.0/24	Default route table	Deploy services.	During/After migration
VPC-C	172.18.0.0/16	subnet-C02	172.18.253.0/29	Default route table	Verify the communications between the VPC and the enterprise router.	During migration

**Table 6** VPC peering connection details
Connection Name	Local VPC	Peer VPC	Connection Is Used to	Phase
peer-AB	VPC-A	VPC-B	Connect subnet-A01 in VPC-A to subnet-B01 in VPC-B.	Before/During migration
peer-AC	VPC-A	VPC-C	Connect subnet-A01 in VPC-A to subnet-C01 in VPC-C.	Before/During migration
peer-BC	VPC-B	VPC-C	Connect subnet-B01 in VPC-B to subnet-C01 in VPC-C.	Before/During migration

**Table 7** ECS details
ECS	VPC	Subnet	Private IP Address	Image	Security Group	ECS Is Used to	Phase
ecs-A01	VPC-A	subnet-A01	172.16.0.139	Public image: CentOS 8.2 64bit	sg-demo (general-purpose web server)	Run your workloads.	Before/During/After migration
ecs-A02	VPC-A	subnet-A02	172.16.253.3			Verify the communications between the VPC and the enterprise router.	During migration
ecs-B01	VPC-B	subnet-B01	172.17.0.93			Run your workloads.	Before/During/After migration
ecs-B02	VPC-B	subnet-B02	172.17.253.4			Verify the communications between the VPC and the enterprise router.	During migration
ecs-C01	VPC-C	subnet-C01	172.18.0.220			Run your workloads.	Before/During/After migration
ecs-C02	VPC-C	subnet-C02	172.18.253.5			Verify the communications between the VPC and the enterprise router.	During migration

**Table 8** Enterprise router details
Name	ASN	Default Route Table Association	Default Route Table Propagation	Auto Accept Shared Attachments	Association Route Table	Attachment	Phase
er-ABC	64512	Enabled	Enabled If your VPC CIDR blocks overlap, do not enable this function.	Disabled If you want to connect VPCs of different accounts using an enterprise router, enable this function. For details, see Sharing Overview.	Default route table	er-attach-A	During/After migration
						er-attach-B
						er-attach-C

**Table 9** VPC attachment details
Name	Type	VPC	Subnet	Auto Add Routes	Phase
er-attach-A	VPC	VPC-A	subnet-A01	Disabled	During/After migration
er-attach-B		VPC-B	subnet-B01
er-attach-C		VPC-C	subnet-C01

Parent topic: Using Enterprise Router to Migrate the Network Set Up Through VPC Peering

Previous topic: Overview

Next topic: Process of Using Enterprise Router to Migrate the Network Set Up Through VPC Peering

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