RFC 7432 defines the use of the sticky bit in the MAC mobility extended community to signal static MAC addresses. These addresses must be protected in case there is an attempt to dynamically learn them in a different place in the EVPN-VXLAN VPLS service.
In the 7750 SR, 7450 ESS, and 7950 XRS, any conditional static MAC defined in an EVPN-VXLAN VPLS service is advertised by BGP-EVPN as a static address, that is, with the sticky bit set. An example of the configuration of a conditional static MAC is shown below:
*A:PE63>config>service>vpls# info
----------------------------------------------
description "vxlan-service"
...
sap 1/1/1:1000 create
exit
static-mac
mac 00:ca:ca:ca:ca:00 create sap 1/1/1:1000 monitor fwd-status
exit
no shutdown
*A:PE64# show router bgp routes evpn mac hunt mac-address 00:ca:ca:ca:ca:00
...
===============================================================================
BGP EVPN Mac Routes
===============================================================================
Network : 0.0.0.0/0
Nexthop : 192.0.2.63
From : 192.0.2.63
Res. Nexthop : 192.168.19.1
Local Pref. : 100 Interface Name : NotAvailable
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : 0
AIGP Metric : None
Connector : None
Community : target:65000:1000 mac-mobility:Seq: 0/Static
Cluster : No Cluster Members
Originator Id : None Peer Router Id : 192.0.2.63
Flags : Used Valid Best IGP
Route Source : Internal
AS-Path : No As-Path
EVPN type : MAC
ESI : 0:0:0:0:0:0:0:0:0:0 Tag : 1063
IP Address : :: RD : 65063:1000
Mac Address : 00:ca:ca:ca:ca:00 Mac Mobility : Seq:0
Neighbor-AS : N/A
Source Class : 0 Dest Class : 0
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
Local static MACs or remote MACs with sticky bit are considered as "protected". A packet entering a SAP / SDP binding is discarded if its source MAC address matches one of these 'protected' MACs.