Remote VCN Peering using a Legacy DRG
This topic is about remote VCN peering. In this case, remote means that the VCNs reside in different regions. If the VCNs you want to connect are in the same region, see Local VCN Peering using Local Peering Gateways.
This article assumes the DRG is a legacy DRG, and we recommend the method described in Remote VCN Peering through an Upgraded DRG for any upgraded DRG. See DRG versions for an explanation of the DRG versions.
Overview of Remote VCN Peering
Remote VCN peering is the process of connecting two VCNs in different regions (but the same tenancy ). Peering lets the VCNs' resources communicate using private IP addresses without routing the traffic over the internet or through an on-premises network. Without peering, a VCN would need an internet gateway and public IP addresses for the instances that need to communicate with another VCN in a different region.
Summary of Networking Components for Remote Peering
At a high level, the Networking service components required for a remote peering include:
-
Two VCNs with CIDRs that don't overlap, in different regions that support remote peering.
Note
All VCN CIDRs Must Not Overlap
The two VCNs in the peering relationship must not have overlapping CIDRs. Also, if a particular VCN has several peering relationships, those other VCNs must not have overlapping CIDRs with each other. For example, if VCN-1 is peered with VCN-2 and also VCN-3, then VCN-2 and VCN-3 must not have overlapping CIDRs.
- A Dynamic Routing Gateway (DRG) attached to each VCN in the peering relationship. A VCN already has a DRG if you're using a Site-to-Site VPN IPSec tunnel or an Oracle Cloud Infrastructure FastConnect private virtual circuit.
- A remote peering connection (RPC) on each DRG in the peering relationship.
- A connection between those two RPCs.
- Supporting route rules to enable traffic to flow over the connection, and only to and from select subnets in the respective VCNs (if required).
- Supporting security rules to control the types of traffic allowed to and from the instances in the subnets that need to communicate with the other VCN.
The following diagram illustrates the components.
A VCN can only use the connected RPCs to reach VNICs in the other VCN or an on-premises network, and not destinations outside of the VCNs such as the internet. For example, if VCN-1 in the preceding diagram were to have an internet gateway, the instances in VCN-2 couldn't use it to send traffic to endpoints on the internet. For more information, see Important Implications of Peering.
Spoke-to-Spoke: Remote Peering with Transit Routing
The scenario this section mentions is still supported, but is deprecated. We recommend you use the DRG Transit routing method described in Routing traffic through a central network virtual appliance.
Imagine that in each region you have several VCNs in a hub-and-spoke layout, as shown in the following diagram. This type of layout within a region is discussed in detail in Transit Routing inside a hub VCN. The spoke VCNs in a particular region are locally peered with the hub VCN in the same region, using local peering gateways .
You can set up remote peering between the two hub VCNs. You can then also set up transit routing for the hub VCN's DRG and LPGs, as discussed in Transit Routing inside a hub VCN. This setup lets a spoke VCN in one region communicate with one or more spoke VCNs in the other region without needing a remote peering connection directly between those VCNs.
For example, you could configure routing so that resources in VCN-1-A could communicate with resources in VCN-2-A and VCN-2-B by way of the hub VCNs. That way, VCN 1-A isn't required to have a separate remote peering with each of the spoke VCNs in the other region. You could also set up routing so that VCN-1-B could communicate with the spoke VCNs in region 2, without needing its own remote peerings to them.
Explicit Agreement Required from Both Sides
Peering between two VCNs requires explicit agreement from both parties in the form of Oracle Cloud Infrastructure Identity and Access Management policies that each party implements for their own VCN's compartment .
Important Remote Peering Concepts
The following concepts help you understand the basics of peering and how to establish a remote peering.
- PEERING
- A peering is a single peering relationship between two VCNs. Example: If VCN-1 peers with two other VCNs, then two peerings exist. The remote part of remote peering indicates that the VCNs are in different regions.
- VCN ADMINISTRATORS
- In general, VCN peering can occur only if both of the VCN administrators agree to it. In practice, this means that the two administrators must:
- ACCEPTOR AND REQUESTOR
- To implement the IAM policies required for peering, the two VCN administrators must select one administrator as the requestor and the other as the acceptor. The requestor must be the one to start the request to connect the two RPCs. In turn, the acceptor must create a particular IAM policy that gives the requestor permission to connect to RPCs in the acceptor's compartment . Without that policy, the requestor's request to connect fails.
- REGION SUBSCRIPTION
- To peer with a VCN in another region, a tenancy must first be subscribed to that region. For information about subscribing, see Managing Regions.
- REMOTE PEERING CONNECTION (RPC)
- A remote peering connection (RPC) is a component you create on the DRG attached to a VCN. The RPC's job is to act as a connection point for a remotely peered VCN. As part of configuring the VCNs, each administrator must create an RPC for the DRG on their VCN. A specific DRG must have a separate RPC for each remote peering it establishes for the VCN. To continue with the previous example: the DRG on VCN-1 would have two RPCs to peer with two other VCNs. In the API, a RemotePeeringConnection is an object that contains information about the peering. You can't reuse an RPC to later establish another peering with it.
- CONNECTION BETWEEN TWO RPCS
- When the requestor starts the request to peer (in the Console or API), they're effectively asking to connect the two RPCs. This means the requestor must have information to identify each RPC (such as the RPC's region and OCID ).
- ROUTING TO THE DRG
- As part of configuring the VCNs, each administrator must update the VCN's routing to enable traffic to flow between the VCNs. For each subnet that needs to communicate with the other VCN, update the subnet's route table. The route rule specifies the destination traffic's CIDR and the DRG as the target. The DRG routes traffic that matches that rule to the other DRG, which in turn routes the traffic to the next hop in the other VCN.
-
Callout 3: Subnet A Route Table Destination CIDR Route Target 0.0.0.0/0 Internet Gateway 192.168.0.0/16 DRG-1 Callout 4: Subnet X Route Table Destination CIDR Route Target 10.0.0.0/16 DRG-2 - SECURITY RULES
- Each subnet in a VCN has one or more security lists that control traffic in and out of the subnet's VNICs at the packet level. You can use security lists to control the type of traffic allowed with the other VCN. As part of configuring the VCNs, each administrator must decide which subnets in their own VCN need to communicate with VNICs in the other VCN and update their subnet's security lists to allow the traffic.
Important Implications of Peering
If you haven't yet, read Important Implications of Peering to understand important access control, security, and performance implications for peered VCNs.
Setting Up a Remote Peering
This section covers the general process for setting up a peering between two VCNs in different regions.
The following procedure assumes that:
- This tenancy is subscribed to the other VCN's region. If it's not, see Managing Regions.
- You already have a DRG attached to the VCN. If you don't, see Dynamic Routing Gateways.
- Create the RPCs: Each VCN administrator creates an RPC for their own VCN's DRG.
- Share information: The administrators share the basic required information.
- Set up the required IAM policies for the connection: The administrators set up IAM policies to enable the connection to be established.
- Establish the connection: The requestor connects the two RPCs (see Important Remote Peering Concepts for the definition of the requestor and acceptor).
- Update route tables: Each administrator updates their VCN's route tables to enable traffic between the peered VCNs or subnets.
- Update security rules: Each administrator updates their VCN's security rules to enable traffic between the peered VCNs or subnets.
The administrators can perform tasks E and F before establishing the connection. Each administrator needs to know the CIDR block or specific subnets from the other VCN and share that in task B.
Each acceptor or requestor administrator creates an RPC for their own VCN's DRG.
Required IAM Policy to Create RPCs
If the administrators already have broad network administrator permissions (see Let network admins manage a cloud network), then they have permission to create, update, and delete RPCs. Otherwise, here's an example policy giving the necessary permissions to a group called RPCAdmins. The second statement is required because creating an RPC affects the DRG it belongs to, so the administrator must have permission to manage DRGs.
Allow group RPCAdmins to manage remote-peering-connections in tenancy
Allow group RPCAdmins to manage drgs in tenancy
See Creating a Remote Peering Connection and Remote Peering Management for general instructions on creating and working with RPCs. If you're the acceptor, record the RPC's region and OCID and share that information with the requestor. If the two VCNs are in different tenancies, each administrator must record their tenancy OCID (found on the very bottom of the page in the Console) and give this information to the other administrator.
When both VCNs are in the same tenancy but different regions, use the policies provided in Remote Peering with a Legacy DRG.
If both VCNs are in different tenancies but the same region, use the policies provided in Attaching to VCNs in Other Tenancies.
The requestor must perform this task.
Prerequisite: The requestor must have:
- The region the acceptor's VCN is in (the requestor's tenancy must be subscribed to the region).
- The OCID of the acceptor's RPC.
See Creating a Remote Peering Connection for general instructions, and use the information provided for the acceptor. See Remote Peering Management for general instructions on working with RPCs.
As mentioned earlier, each administrator can do this task before or after the connection is established.
Prerequisite: Each administrator must have the VCN CIDR block or the CIDR block for specific subnets in the other VCN.
For each VCN, decide which subnets in the VCN need to communicate with the other VCN and update the route table (see Updating a VCN Route Table's Rules) for each of those subnets to include a new route rule that directs traffic destined for the other VCN to the DRG:
- Target Type: Dynamic Routing Gateway. The VCN's attached DRG is automatically selected as the target, and you don't have to specify the target yourself.
- Destination CIDR Block: The other VCN's CIDR block. If you want, you can specify a subnet or particular subset of the peered VCN's CIDR.
- Description: An optional description of the rule.
Any subnet traffic with a destination that matches the rule is routed to the DRG. For more information about VCN route tables and rules, see VCN Route Tables.
Without the required routing, traffic doesn't flow between the peered DRGs. If a situation occurs where you need to temporarily stop the peering, temporarily remove the route rules that enable traffic. You don't need to delete the RPCs.
As mentioned earlier, each administrator can do this task before or after the connection is established.
Prerequisite: Each administrator must know the CIDR block or specific subnets to share with the other VCN. In general, use the same CIDR block you used in the route table rule in Task E: Configure the route tables.
Add the following rules:
- Ingress rules for the types of traffic you want to allow from the other VCN, either from the VCN's CIDR or only specific subnets.
- Egress rule to allow outgoing traffic from the local VCN to the other VCN. If the subnet already has a broad egress rule for all types of protocols to all destinations (such as 0.0.0.0/0), then you don't need to add a special one for the other VCN.
The following procedure uses security lists, but you could instead implement the security rules in a network security group and then create the subnet's resources in that NSG.
For the local VCN, decide which subnets in the VCN need to communicate with the other VCN and update the security list for each of those subnets to include rules that allow the egress or ingress traffic with the CIDR block or subnet of the other VCN:
For more information about security rules, see Security Rules.
Let's say you want to add a stateful rule that allows ingress HTTPS (port 443) traffic from the other VCN's CIDR. Here are the basic steps you take when adding a rule:
- In the Allow Rules for Ingress section, select +Add Rule.
- Leave the Stateless checkbox unselected.
- Source Type: Leave as CIDR.
- Source CIDR: Enter the same CIDR block that the route rules use (see Task E: Configure the route tables).
- IP Protocol: Leave as TCP.
- Source Port Range: Leave as All.
- Destination Port Range: Enter 443.
- Description: An optional description of the rule.