If using Transit Hub service, a single gateway acting as a central hub allows multiple VPCs to form a centralized connection and an environment capable of communicating between VPCs. The service can eliminate complex peering relationships, centralize and simplify your network, and act as a router to manage communication paths between VPCs. Transit Hub is only available in new network environments for Korea (Pangyo) region. Projects created by Korea (Pangyo) region before March 7, 2022 are network environments before improvement, so you need to create new projects to use Transit Hub.
When multicast communication between VPCs is required
It is a top-level resource that manages centralized connections and provides routing and multicast communication between connected resources.
A resource that manages the association relationship between the Transit Hub and other resources. Currently, only attachment that is connected to the VPC is available.
Select attachment to forward packets based on the destination IP address of the packet and act as a router to forward packets. Depending on the settings that you enter when you create a Transit Hub, you can have one default routing table and if you need additional routing tables, you can create additional routing tables.
These settings that specify attachment to which packets will flow into the routing table. Packets that flown into the routing table by routing association are forwarded to another attachment by routing rule. One attachment can only create one routing association from one routing table.
Obtain the CIDR value of the resource associated with attachment and automatically create routing rule.
This is a route policy included in the routing table. Set up static routing by specifying the destination CIDR and the attachment to which the packet is forwarded. Regardless of whether or not the routing association is created, you can designate the route of all attachments of the same transit hub and forward packets
[Note] All attachments under the same transit hub can be used as the next hop in the routing rule.
You can split a Transit Hub into multiple multicast domains and multicast domains will have multicast networks independent of one another.
This is a setting to connect attachment and multicast domain. The subnet related to the VPC associated with the attachment will join the connected multicast network.
[Note] One subnet can only be attached to one multicast domain.
This means the set of VM instances that uses the same multicast IP address in the multicast domain. You can add network interface of VM instance that uses a subnet connected to a multicast domain as a multicast group.