BGP dynamic routing¶

Available since MOSK 23.2 TechPreview

The BGP dynamic routing extension to the Networking service (OpenStack Neutron) is particularly useful for the MOSK clouds where private networks managed by cloud users need to be transparently integrated into the networking of the data center.

For example, the BGP dynamic routing is a common requirement for IPv6-enabled environments, where clients need to seamlessly access cloud workloads using dedicated IP addresses with no address translation involved in between the cloud and the external network.

Untitled Diagram

BGP dynamic routing changes the way self-service (private) network prefixes are communicated to BGP-compatible physical network devices, such as routers, present in the data center. It eliminates the traditional reliance on static routes or ICMP-based advertising by enabling the direct passing of private network prefix information to router devices.

Note

To effectively use the BGP dynamic routing feature, Mirantis recommends acquiring good understanding of OpenStack address scopes and how they work.

The components of the OpenStack BGP dynamic routing are:

Service plugin
An extension to the Networking service (OpenStack Neutron) that implements the logic for BGP-related entities orhestration and provides the cloud user-facing API. A cloud administrator creates and configures a BGP speaker using the CLI or API and manually schedules it to one or more hosts running the agent.
Agent
Manages BGP peering sessions. In MOSK, the BGP agent runs on nodes labeled with openstack-gateway=enabled.

Prefix advertisement depends on the binding of external networks to a BGP speaker and the address scope of external and internal IP address ranges or subnets.

Prefix advertisement¶

BGP dynamic routing advertises prefixes for self-service networks and host routes for floating IP addresses.

To successfully advertise a self-service network, you need to fulfill the following conditions:

External and self-service networks reside in the same address scope.
The router contains an interface on the self-service subnet and a gateway on the external network.
The BGP speaker associates with the external network that provides a gateway on the router.
The BGP speaker has the advertise_tenant_networks attribute set to True.

To successfully advertise a floating IP address, you need to fulfill the following conditions:

The router with the floating IP address binding contains a gateway on an external network with the BGP speaker association.
The BGP speaker has the advertise_floating_ip_host_routes attribute set to true.

The diagram below is an example of the BGP dynamic routing in the non-DVR mode with self-service networks and the following advertisements:

B>* 192.168.0.0/25 [200/0] through 10.11.12.1
B>* 192.168.0.128/25 [200/0] through 10.11.12.2
B>* 10.11.12.234/32 [200/0] through 10.11.12.1

Untitled Diagram

Operation in the Distributed Virtal Router (DVR) mode¶

For both floating IP and IPv4 fixed IP addresses, the BGP speaker advertises the gateway of the floating IP agent on the corresponding compute node as the next-hop IP address. When using IPv6 fixed IP addresses, the BGP speaker advertises the DVR SNAT node as the next-hop IP address.

The diagram below is an example of the BGP dynamic routing in the DVR mode with self-service networks and the following advertisements:

B>* 192.168.0.0/25 [200/0] through 10.11.12.1
B>* 192.168.0.128/25 [200/0] through 10.11.12.2
B>* 10.11.12.234/32 [200/0] through 10.11.12.12

Untitled Diagram