Based on the result of the DF election or the manual service-carving, the control plane on the non-DF (PE1) instructs the datapath to remove the LAG SAP (associated with the ESI) from the default flooding list for BM traffic (unknown unicast traffic may still be sent if the EVI label is a unicast label and the source MAC address is not associated to the ESI). On PE1 and PE2, both LAG SAPs learn the same MAC address (coming from the CE).
For example, in the following sample configuration output, 00:ca:ca:ba:ce:03 is learned on both PE1 and PE2 access LAG (on ESI-1). However, PE1 learns the MAC as ‟Learned” whereas PE2 learns it as ‟Evpn”. This is because CE2 hashes the traffic for that source MAC to PE1. And PE2 learns the MAC through EVPN but associates the MAC to the ESI SAP, because the MAC belongs to the ESI.
*A:PE1# show service id 1 fdb detail
===============================================================================
Forwarding Database, Service 1
===============================================================================
ServId MAC Source-Identifier Type Last Change
Age
-------------------------------------------------------------------------------
1 00:ca:ca:ba:ce:03 sap:lag-1:1 L/0 06/11/15 00:14:47
1 00:ca:fe:ca:fe:70 eMpls: EvpnS 06/11/15 00:09:06
192.0.2.70:262140
1 00:ca:fe:ca:fe:72 eMpls: EvpnS 06/11/15 00:09:39
192.0.2.72:262141
-------------------------------------------------------------------------------
No. of MAC Entries: 3
-------------------------------------------------------------------------------
Legend: L=Learned O=Oam P=Protected-MAC C=Conditional S=Static
===============================================================================
*A:PE2# show service id 1 fdb detail
===============================================================================
Forwarding Database, Service 1
===============================================================================
ServId MAC Source-Identifier Type Last Change
Age
-------------------------------------------------------------------------------
1 00:ca:ca:ba:ce:03 sap:lag-1:1 Evpn 06/11/15 00:14:47
1 00:ca:fe:ca:fe:69 eMpls: EvpnS 06/11/15 00:09:40
192.0.2.69:262141
1 00:ca:fe:ca:fe:70 eMpls: EvpnS 06/11/15 00:09:40
192.0.2.70:262140
-------------------------------------------------------------------------------
No. of MAC Entries: 3
-------------------------------------------------------------------------------
Legend: L=Learned O=Oam P=Protected-MAC C=Conditional S=Static
===============================================================================
When PE1 (non-DF) and PE2 (DF) exchange BUM packets for evi 1, the packets are sent including the ESI label at the bottom of the stack (in both directions). The ESI label advertised by each PE for ESI-1 can be displayed using the following command.
*A:PE1# show service system bgp-evpn ethernet-segment name "ESI-1"
===============================================================================
Service Ethernet Segment
===============================================================================
Name : ESI-1
Admin State : Up Oper State : Up
ESI : 01:00:00:00:00:71:00:00:00:01
Multi-homing : allActive Oper Multi-homing : allActive
Lag Id : 1
ES Activation Timer : 0 secs
Exp/Imp Route-Target : target:00:00:00:00:71:00
Svc Carving : auto
ES SHG Label : 262142
===============================================================================
*A:PE2# show service system bgp-evpn ethernet-segment name "ESI-1"
===============================================================================
Service Ethernet Segment
===============================================================================
Name : ESI-1
Admin State : Up Oper State : Up
ESI : 01:00:00:00:00:71:00:00:00:01
Multi-homing : allActive Oper Multi-homing : allActive
Lag Id : 1
ES Activation Timer : 20 secs
Exp/Imp Route-Target : target:00:00:00:00:71:00
Svc Carving : auto
ES SHG Label : 262142
===============================================================================