Juniper T1600 Hardware Manual page 238

T1600 Core Router Hardware Guide
Table 41: Effect of Taking the Host Subsystem Offline (continued)
Master host subsystem
214
The backup host subsystem becomes the master. The backup Routing Engine assumes Routing
Engine functions. The master host subsystem is hot-pluggable. Removal or failure of the master
Routing Engine affects forwarding and routing based on the high availability configuration:
Dual Routing Engines without any high availability features enabled—Traffic is interrupted
while the Packet Forwarding Engine is reinitialized. All kernel and forwarding processes are
restarted. When the switchover to the new master Routing Engine is complete, routing
convergence takes place and traffic is resumed.
Graceful Routing Engine switchover (GRES) is enabled—Graceful Routing Engine switchover
preserves interface and kernel information. Traffic is not interrupted. However, graceful Routing
Engine switchover does not preserve the control plane. Neighboring routers detect that the
router has restarted and react to the event in a manner prescribed by individual routing protocol
specifications. To preserve routing without interruption during a switchover, graceful Routing
Engine switchover must be combined with nonstop active routing.
Nonstop active routing is enabled (graceful Routing Engine switchover must be configured for
nonstop active routing to be enabled)—Nonstop active routing supports Routing Engine
switchover without alerting peer nodes that a change has occurred. Nonstop active routing
uses the same infrastructure as graceful Routing Engine switchover to preserve interface and
kernel information. However, nonstop active routing also preserves routing information and
protocol sessions by running the routing protocol process (rpd) on both Routing Engines. In
addition, nonstop active routing preserves TCP connections maintained in the kernel.
Nonstop active routing is supported on Junos OS Release 8.5 and later for standalone T1600
routers, Junos OS Release 10.0 and later for T1600 routers in a routing matrix.
Graceful restart is configured—Graceful restart provides extensions to routing protocols so
that neighboring helper routers restore routing information to a restarting router. These
extensions signal neighboring routers about the graceful restart and prevent the neighbors
from reacting to the router restart and from propagating the change in state to the network
during the graceful restart period. Neighbors provide the routing information that enables the
restarting router to stop and restart routing protocols without causing network reconvergence.
Neighbors are required to support graceful restart. The routing protocol process (rpd) restarts.
A graceful restart interval is required. For certain protocols, a significant change in the network
can cause graceful restart to stop.
NOTE: Router performance might change if the backup Routing Engine's
configuration differs from the former master's configuration. For the most
predictable performance, configure the two Routing Engines identically,
except for parameters unique to each Routing Engine.
NOTE: For information about configuring graceful switchover and nonstop
active routing, see the Junos OS High Availability Configuration Guide.
To take a host subsystem offline:
Determine whether the host subsystem is functioning as the master or as the backup,
1.
using one of the two following methods:
Check the Routing Engine LEDs on the craft interface. If the green
lit, the corresponding host subsystem is functioning as the master.
Issue the following CLI command. The master Routing Engine is designated
in the Current state field:
MASTER LED is
Copyright © 2010, Juniper Networks, Inc.
Master