IBM Cloud Transit Gateway overview
With IBM Cloud® Transit Gateway (TGW), you can create a single or multiple transit gateways to connect VPCs together. You can also connect your IBM Cloud classic infrastructure to a Transit Gateway to provide seamless communication with Classic Infrastructure resources. Any new network that you connect to a Transit Gateway is then automatically made available to every other network connected to it.
IBM Cloud Transit Gateway supports local and global routing between VPCs and the IBM Cloud classic infrastructure. Connections to and from an IBM Cloud Transit Gateway on the IBM private network are not shown to the public internet. This arrangement reduces public egress and VPN costs and reduces security threats. IBM Cloud Transit Gateway is a fully redundant, fault-tolerant service with no single point of failure within IBM Cloud multizone regions.
IBM Cloud Transit Gateway provisions and defines connections between resources on the IBM Cloud network, providing private interconnectivity between IBM Cloud data centers worldwide. It also provides a central hub for connectivity to provision and manage your networks. With IBM Cloud Transit Gateway, you can create a single Transit Gateway or multiple transit gateways to connect IBM Cloud VPCs. You can also connect your IBM Cloud classic infrastructure to a Transit Gateway to provide seamless communication with classic infrastructure resources. Any new resource that you connect to a Transit Gateway is automatically made available to every other resource connected to it. All data remains within the private IBM Cloud backbone and is optimized for performance.
For more information, see About IBM Cloud Transit Gateway.
Considerations with VMware Cloud Foundation for VPC
When you use Transit Gateway with your VMware® solution on VPC, the routing differs slightly between the two networking architectures.
When you use VMware virtual machines (VMs) on the VPC subnet architecture, your VMs are attached to VPC subnets and the routing behaves in the same way as with VPC Virtual Servers. The VPC subnets are provisioned from the zone prefix, and when the VPC is attached to a Transit Gateway, the routing works between other VPCs without any required changes. If you are using IANA-registered IP addresses in your VPC, see Routing considerations for IANA-registered IP assignments.
When you use NSX™ on your VMware solution on VPC, the VMs are attached on the NSX overlay segments. They use an IP address range or prefix, which is reachable through VPC route that points to the NSX Tier-0 private uplink VIP as described in VMware NSX logical routing on VPC. When you attach the VPC to a Direct Link, you must create the VPC routes with advertise flag so that they are advertised.
