Juniper JUNOS 10.1 - CONFIGURATION GUIDE 1-2010 Configuration Manual page 109

underlying logical interfaces, and brings down the working link and its underlying
logical interfaces, causing the routing protocols to reconverge. This consumes time
and leads to traffic loss even though the APS infrastructure has performed the switch
quickly.
Container Interfaces Concept
To solve this problem, the JUNOS Software provides a soft interface construct called
a container interface (see Figure 2 on page 39).
Figure 2: Container Interface
The container interface allows routing protocols to run on the logical interfaces
associated with a virtual container interface instead of on the physical SONET
interfaces. When APS switches the underlying physical link based on a fault condition,
the container interface remains up, and the logical interface on the container interface
does not flap. The routing protocols remain unaware of the APS switching.
APS Support for Container-Based Interfaces
With the container interface, APS is configured on the container interface itself.
Individual member SONET links are either marked as primary (corresponding to the
working circuit) or standby (corresponding to the protect circuit) in the configuration.
No circuit or group name is specified in the container interface model; physical
SONET links are put in an APS group by linking them to a single container interface.
APS parameters are specified at the container interface level, and are propagated to
the individual SONET links by the APS daemon.
Autocopy of APS Parameters
Typical applications require copying APS parameters from the working circuit to the
protect circuit, since most of the parameters must be the same for both circuits. This
is automatically done in the container interface. APS parameters are specified only
once under the container physical interface configuration, and are internally copied
over to the individual physical SONET links.
Chapter 2: Understanding Router Interfaces
Container Interfaces Overview
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