The EVPN-VXLAN service is designed around the current VPLS objects and the additional VXLAN construct.
Figure 1 shows a DC with a Layer 2 service that carries the traffic for a tenant who wants to extend a subnet beyond the DC. The DC PE function is carried out by the 7750 SR, 7450 ESS, and 7950 XRS where a VPLS instance exists for that particular tenant. Within the DC, the tenant has VPLS instances in all the Network Virtualization Edge (NVE) devices where they require connectivity (such VPLS instances can be instantiated in TORs, Nuage VRS, VSG, and so on). The VPLS instances in the redundant DGW and the DC NVEs are connected by VXLAN bindings. BGP-EVPN provides the required control plane for such VXLAN connectivity.
The DGW routers are configured with a VPLS per tenant that provides the VXLAN connectivity to the Nuage VPLS instances. On the router, each tenant VPLS instance is configured with:
The WAN-related parameters (SAPs, spoke SDPs, mesh-SDPs, BGP-AD, and so on).
The BGP-EVPN and VXLAN (VNI) parameters. The following CLI output shows an example for an EVPN-VXLAN VPLS service.
*A:DGW1>config>service>vpls# info
----------------------------------------------
description "vxlan-service"
vxlan instance 1 vni 1 create
exit
bgp
route-distinguisher 65001:1
route-target export target:65000:1 import target:65000:1
exit
bgp-evpn
unknown-mac-route
mac-advertisement
vxlan bgp 1 vxlan-instance 1
no shutdown
exit
sap 1/1/1:1 create
exit
no shutdown
----------------------------------------------
The bgp-evpn context specifies the encapsulation type (only vxlan is supported) to be used by EVPN and other parameters like the unknown-mac-route and mac-advertisement commands. These commands are typically configured in three different ways:
no unknown-mac-route and mac-advertisement (default option) — The router advertises new learned MACs (on the SAPs or SDP bindings) or new conditional static MACs.
unknown-mac-route and no mac-advertisement — The router only advertises an unknown-mac-route as long as the service is operationally up (if no BGP-MH site is configured in the service) or the router is the DF (if BGP-MH is configured in the service).
unknown-mac-route and mac-advertisement — The router advertises new learned MACs, conditional static MACs, and the unknown-mac-route. The unknown-mac-route is only advertised under the preceding described conditions.
Other parameters related to EVPN or VXLAN are:
MAC duplication parameters
The vxlan vni defines the VNI that the router uses in the EVPN routes generated for the VPLS service.
After the VPLS is configured and operationally up, the router sends or receives inclusive multicast Ethernet Tag routes, and a full-mesh of VXLAN connections are automatically created. These VXLAN ‟auto-bindings” can be characterized as follows:
The VXLAN auto-binding model is based on an IP-VPN-like design, where no SDPs or SDP binding objects are created by or visible to the user. The VXLAN auto-binds are composed of remote VTEPs and egress VNIs, and can be displayed with the following command:
A:PE-1# show service id 40 vxlan destinations
===============================================================================
Egress VTEP, VNI
===============================================================================
Instance VTEP Address Egress VNI Evpn/ Num.
Mcast Oper State L2 PBR Static MACs
-------------------------------------------------------------------------------
1 192.0.2.1 40 evpn 0
BUM Up No
1 192.0.2.3 40 evpn 1
BUM Up No
-------------------------------------------------------------------------------
Number of Egress VTEP, VNI : 2
-------------------------------------------------------------------------------
===============================================================================
===============================================================================
BGP EVPN-VXLAN Ethernet Segment Dest
===============================================================================
Instance Eth SegId Num. Macs Last Change
-------------------------------------------------------------------------------
No Matching Entries
===============================================================================
The VXLAN bindings observe the VPLS split-horizon rule. This is performed automatically without the need for any split-horizon configuration.
BGP Next-Hop Tracking for EVPN is fully supported. If the BGP next-hop for a specified received BGP EVPN route disappears from the routing table, the BGP route is not marked as ‟used” and the respective entry in show service id vxlan destinations is removed.
After the flooding domain is setup, the routers and DC NVEs start advertising MAC addresses, and the routers can learn MACs and install them in the FDB. Some considerations are the following:
All the MAC addresses associated with remote VTEP/VNIs are always learned in the control plane by EVPN. Data plane learning on VXLAN auto-bindings is not supported.
When unknown-mac-route is configured, it is generated when no (BGP-MH) site is configured, or a site is configured AND the site is DF in the PE.
The unknown-mac-route is not installed in the FDB (therefore, does not show up in the show service id svc-id fdb detail command).
While the router can be configured with only one VNI (and signals a single VNI per VPLS), it can accept any VNI in the received EVPN routes as long as the route target is properly imported. The VTEPs and VNIs show up in the FDB associated with MAC addresses:
A:PE65# show service id 1000 fdb detail
===============================================================================
Forwarding Database, Service 1000
===============================================================================
ServId MAC Source-Identifier Type Last Change
Age
-------------------------------------------------------------------------------
1000 00:00:00:00:00:01 vxlan-1: Evpn 10/05/13 23:25:57
192.0.2.63:1063
1000 00:00:00:00:00:65 sap:1/1/1:1000 L/30 10/05/13 23:25:57
1000 00:ca:ca:ca:ca:00 vxlan-1: EvpnS 10/04/13 17:35:43
192.0.2.63:1063
-------------------------------------------------------------------------------
No. of MAC Entries: 3
-------------------------------------------------------------------------------
Legend: L=Learned O=Oam P=Protected-MAC C=Conditional S=Static
===============================================================================