High Availability and Virtualization Features in the Junos OS

In support of high-availability router functioning, the Junos OS includes the following features:

• Graceful restart—Enables a routing protocol, before it restarts, to inform its adjacent neighbors and peers of its condition. Most Junos routing protocols support graceful restart.
• Graceful Routing Engine switchover—On routers with dual Routing Engines, enables switching of mastership between Routing Engines without interruption to packet forwarding.

  For routers in which Adaptive Services, Multiservices, or Tunnel Services PICs or DPCs are installed, features that rely on their services are interrupted momentarily during a Routing Engine switchover. Features that do not use the services continue uninterrupted. After switchover, all features are restored and packet forwarding continues.

The Junos OS supports these virtualization features:

• Unicast reverse-path forwarding.
• Routing instances, which enable you to create multiple instances of BGP, IS-IS, OSPF, PIM, RIP, and static routes.
• Logical systems, which enables you to create multiple logical routing devices within a single router.