(Optional) Configuring VXLAN Gateways to Advertise Specific Types of Routes

To enable communication between VMs on different subnets, configure VXLAN gateways to exchange IRB or IP prefix routes. This configuration enables the gateways to learn the IP routes of the related hosts or the subnets where the hosts reside.

Context

By default, VXLAN gateways can exchange MAC routes, but must be configured to exchange IRB or IP prefix routes if VMs need to communicate across subnets. If an RR is deployed on the network, IRB or IP prefix routes must be exchanged only between the VXLAN gateways and RR.

Host routes can be advertised through IRB routes (recommended), IP prefix routes, or both. In contrast, subnet routes of hosts can be advertised through IP prefix routes only.

Procedure

Configure IRB route advertisement.
1. Run system-view
  The system view is displayed.
2. Run bgp as-number
  The BGP view is displayed.
3. Run l2vpn-family evpn
  The BGP-EVPN address family view is displayed.
4. Run one of the following commands based on the overlay network type to configure IRB route advertisement:
  - For an IPv4 overlay network, run the peer { ipv6-address | group-name } advertise irb command.
  - For an IPv6 overlay network, run the peer { ipv6-address | group-name } advertise irbv6 command.
5. Run commit
  The configuration is committed.
Configure IP prefix route advertisement.
1. Run system-view
  The system view is displayed.
2. Run bgp as-number
  The BGP view is displayed.
3. Run either of the following commands based on the overlay network type:
  - For an IPv4 overlay network, run ipv4-family vpn-instance vpn-instance-name
    The BGP-VPN instance IPv4 address family view is displayed.
  - For an IPv6 overlay network, run ipv6-family vpn-instance vpn-instance-name
    The BGP-VPN instance IPv6 address family view is displayed.
4. Run either of the following commands based on the overlay network type:
  - For an IPv4 overlay network, run import-route { direct | isis process-id | ospf process-id | rip process-id | static } [ med med | route-policy route-policy-name ] ^*
    Routes of other protocols are imported to the BGP-VPN instance IPv4 address family.
  - For an IPv6 overlay network, run import-route { direct | isis process-id | ospfv3 process-id | ripng process-id | static } [ med med | route-policy route-policy-name ] ^*
    Routes of other protocols are imported to the BGP-VPN instance IPv6 address family.
  To advertise host IP routes, configure import of direct routes. To advertise the route to the subnet where hosts reside, configure a dynamic routing protocol (such as OSPF or OSPFv3) and then run either of the preceding commands based on the overlay network type to import the route into the dynamic routing protocol.
5. Run advertise l2vpn evpn
  IP prefix route advertisement is configured.
  
  IP prefix routes are used to advertise host IP routes as well as the route to the subnet where the hosts reside. If many specific host routes exist, a VXLAN gateway can be configured to advertise an IP prefix route, which carries the routing information of the subnet where the hosts reside. After route advertisement, import the route to the target BGP-VPN instance address family, as this reduces the number of routes to be saved on the involved VXLAN gateway.
  - A VXLAN gateway can advertise subnet routes only if the attached subnets are unique across the entire network.
  - After IP prefix route advertisement is configured, run the arp vlink-direct-route advertise or nd vlink-direct-route advertise command to advertise host routes. After this configuration, VM migration is restricted.
6. Run commit
  The configuration is committed.