High availability features include Routing Engine redundancy,
graceful Routing Engine switchover (GRES), nonstop bridging, nonstop
active routing, graceful restart for routing protocols, Virtual Router
Redundancy Protocol (VRRP), and unified in-service software upgrade
(ISSU). Some high availability features are not supported by all platforms
and all PICs. For information about the first supported Junos OS Release
for these features by PIC and platform, see the Junos OS High Availability Configuration Guide
.