ARP and ND (MACIP) Route Exchange

ARP and Neighbor Discovery (ND) addresses that are learned on the VLAN or Bridge Domain and added to EVPN are automatically exported into BGP. ARP and ND routes are referred to as MACIP (type 2) in RFC 7432.

The following types of ARP and ND routes are exported into BGP:

• Dynamically learned routes on VE interfaces with a local egress interface
• Statically configured routes on VE interfaces with a local egress interface
• IPv4 and IPv6 addresses configured on VE interfaces
• Virtual IPv4 and IPv6 addresses configured by means of VRRP or anycast gateway

If ARP or ND is learned with an egress interface as an MCT client interface, the corresponding ESI is attached to the MACIP route.

The resolution of ARP and ND received from BGP EVPN is based on the resolution of the corresponding MAC route. In addition, MAC route movement triggers the movement of MACIP routes. ARP and ND routes are withdrawn from BGP when the MAC resolution changes from a local egress interface to a tunnel.

Statically configured ARP and ND entries carry a sticky flag in the MAC mobility extended community and are installed as static ARP and ND on the routers importing this route. When an ARP or ND entry is sticky, the binding of the host address does not change on a local learning event.

Table 1. MACIP route fields and descriptions

Field	Description
Route Distinguisher	Either an auto or manual RD value is used, depending on the VLAN or bridge domain configuration under EVPN.
ESI	In case the MAC address is learned on an MCT client interface, the ESI of the client interface is present. Otherwise it is 0.
Ethernet Tag	This field is 0.
MAC address	This is the MAC address associated with the ARP or ND.
IP address	This is the IPv4 or IPv6 host address.
MPLS Label1	This is the L2 VNI in case of VXLAN and the EVI label for MPLS.
MPLS Label2	This is conditionally the VRF or Layer 3 VNI. If ARP or ND is learned on a non-default VRF and the VRF is configured to export routes into EVPN, the following behavior applies: The MPLS Label2 field carries the Layer 3 VNI in case of VXLAN, and the VRF label in case of MPLS. Otherwise, Label2 is not sent in the route. Both IP VRF RTs and VLAN/BD RTs are attached. VRRP and anycast gateway addresses are advertised with BGP default gateway extended community. They are used for logging errors when a MACIP route is imported but the same anycast IP address is not configured.

All EVPN MACIP routes are held in the ARP suppression cache, and this database is used for ARP suppression and conversational ARP.

ARP and ND suppression

When an ARP or ND binding for a host address is known in the control plane, the suppression feature allows a router to respond to the ARP or ND requests received on edge ports according to the control plane information rather than flooding the ARP and ND requests in the overlay network. This suppression prevents a significant amount of flooded traffic in the overlay network.

You can enable ARP and ND suppression on a VLAN or bridge domain. For more information, see ARP Suppression and IPv6 Neighbor Discovery Suppression.

By default ARP and ND suppression are disabled.

Note

This behavior applies to both VXLAN and MPLS.