Enterprise Edition transit routers support route synchronization, which enables Enterprise Edition transit routers to automatically advertise routes to network instances. This topic describes the limits on route synchronization, how route synchronization works, and how to enable and disable route synchronization.
Limits
Only Enterprise Edition transit routers support route synchronization.
If a VPC is connected to multiple Enterprise Edition transit routers, you can enable route synchronization only for one of the Enterprise Edition transit routers.
If a VPC is connected to a Basic Edition transit router and an Enterprise Edition transit router, you cannot enable route synchronization for the VPC.
If a VPC is associated with a VPN gateway over an IPsec-VPN connection, you cannot enable route synchronization for the VPC.
After route synchronization is enabled, the Enterprise Edition transit router advertises routes to the network instance. The routes cannot be deleted from the network instance.
The routes advertised from an Enterprise Edition transit router to a VPC consume the route quota on the VPC route table.
Each route table of a VPC supports at most 200 custom routes. You can request a quota increase on the Quota Management page in the VPC console or in the Quota Center console. For more information, see Manage VPC quotas and Submit an application to increase a quota.
The following table describes the limits on route synchronization.
Item
Default value
Adjustable
The maximum number of VPCs that can have route synchronization enabled when the VPCs are connected to the same Enterprise Edition transit router
50
No
How route synchronization works
After you connect a network instance to a Basic Edition transit router, the Basic Edition transit router automatically advertises the routes in its default route table to the route table of the network instance.
After you connect a network instance to an Enterprise Edition transit router, the Enterprise Edition transit router does not advertise routes to the network instance if route synchronization is disabled. You can enable route synchronization for the network instance to enable the Enterprise Edition transit router to automatically advertise routes to the network instance.
The following section describes how route synchronization works for different network instances:
VPC
After you enable route synchronization for a VPC, the Enterprise Edition transit router automatically advertises the routes in the transit router route table that is associated with the VPC to all the route tables of the VPC.
Express Connect Router (ECR)
After you enable route synchronization for an ECR, the Enterprise Edition transit router automatically advertises the routes in the transit router route table that is associated with the ECR to the route table of the ECR.
ImportantIf a route prefix is specified for the transit router in the Express Connect console, only the specified route prefix is advertised to the ECR. Specific routes in the route table of the transit router are not advertised to the ECR. For more information, see Create and manage an ECR.
IPsec-VPN connection
NoteRoute synchronization takes effect only for IPsec-VPN connections that use BGP dynamic routing.
After you enable route synchronization for an IPsec-VPN connection, the Enterprise Edition transit router automatically advertises the routes in the transit router route table that is associated with the IPsec-VPN connection to the BGP route table of the IPsec-VPN connection.
Virtual border router (VBR)
After you enable route synchronization for a VBR, the Enterprise Edition transit router automatically advertises the routes in the transit router route table that is associated with the VBR to the route table of the VBR.
Inter-region connection
After you enable route synchronization for an inter-region connection, the local Enterprise Edition transit router automatically advertises the routes in the transit router route table that is associated with the inter-region connection to the peer Enterprise Edition transit router.
Enable route synchronization
You can enable route synchronization for a network instance when you create the network instance, or after you create a connection on the network instance.
Enable route synchronization when creating a network connection
ECR
When you create an ECR connection, Automatically Advertise Routes to ECR is enabled by default in Advanced Settings and cannot be disabled. For more information, see Create an ECR connection.
IPsec-VPN connection
When you create an IPsec-VPN connection, select Automatically Advertise Routes to VPN in Advanced Settings. For more information, see Create an IPsec-VPN connection.
VBR
When you create a VBR connection, you can turn on Propagate Routes to VB in Advanced Settings to enable automatic route synchronization for the VBR. For more information, see Create a VBR connection.
Inter-region connection
When you create an inter-region connection, select Automatically Advertise Routes to Peer Region in Advanced Settings. For more information, see Use an Enterprise Edition transit router to create an inter-region connection.
You can enable route synchronization for VPCs only after you attach the VPCs to Enterprise Edition transit routers.
Enable route synchronization for a network instance
Before you enable route synchronization for a network instance, make sure that the network instance is associated with a route table of the Enterprise Edition transit router to which the network instance is connected. For more information, see Create an associated forwarding correlation.
You can use one of the following methods to enable route synchronization for a VBR or an IPsec-VPN connection. VPCs support only Method 1. Inter-region connections support only Method 2.
Method 1: Enable route synchronization for a network instance
Log on to the CEN console.
On the Instances page, find and click the CEN instance that you want to manage.
Choose , find the transit router that you want to manage, and then click the ID of the transit router.
On the Intra-region Connections tab, find the connection that you want to manage and enable route synchronization in the Route Synchronization column.
After you enable route synchronization for a network instance, the Enterprise Edition transit router connected to the network instance automatically advertises its routes to the network instance. You can click Details in the Route Synchronization column to view route synchronization details on the Network Instance Route Table tab.
Method 2: Enable route synchronization for a network instance
Log on to the CEN console.
On the Instances page, find and click the CEN instance that you want to manage.
Choose , find the transit router that you want to manage, and then click the ID of the transit router.
On the details page of the transit router, find the VBR connection, IPsec-VPN connection, or inter-region connection that you want to manage and click its ID.
On the Intra-region Connections tab, find the VBR connection or IPsec-VPN connection that you want to manage.
On the Cross-region Connections tab, find the inter-region connection that you want to manage.
In the Attachment Details panel, find the Basic Information section and click Enable next to Automatic Route Advertisement.
In the Enable Automatic Route Advertisement message, click OK.
Disable route synchronization
After you disable route synchronization for a network instance, the Enterprise Edition transit router connected to the network instance automatically withdraws routes from the network instance. Before you disable route synchronization, make sure that your network has a redundant route. Otherwise, network connections may be interrupted after route synchronization is disabled.
When you create a VPC connection, if you allow the system to add routes whose destination CIDR blocks are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 to all the route tables of the VPC, these routes are not withdrawn.
You can use one of the following methods to disable route synchronization for a VBR or an IPsec-VPN connection. VPCs support only Method 1. Inter-region connections support only Method 2.
Method 1: Disable route synchronization for a network instance
Log on to the CEN console.
On the Instances page, find and click the CEN instance that you want to manage.
Choose , find the transit router that you want to manage, and then click the ID of the transit router.
On the Intra-region Connections tab, find the connection that you want to manage and disable route synchronization in the Route Synchronization column.
Method 2: Disable route synchronization for a network instance
Log on to the CEN console.
On the Instances page, find and click the CEN instance that you want to manage.
Choose , find the transit router that you want to manage, and then click the ID of the transit router.
On the details page of the transit router, find the VBR connection, IPsec-VPN connection, or inter-region connection that you want to manage and click its ID.
On the Intra-region Connections tab, find the VBR connection or IPsec-VPN connection that you want to manage.
On the Cross-region Connections tan, find the inter-region connection that you want to manage.
In the Attachment Details panel, find the Basic Information section and click Disable next to Automatic Route Advertisement.
In the Disable Automatic Route Advertisement message, click OK.