Line Module Forwarding Plane Upgrade - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - SERVICE AVAILABILITY CONFIGURATION GUIDE 2010-10-08 Configuration Manual

JunosE 11.3.x Service Availability Configuration Guide
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When the primary SRP module has verified that all line modules are up, the redundant
SRP module takes over control of the router by becoming the active SRP module. The
primary, and formerly active, SRP module reboots to the armed release and serves as
the standby SRP module.
All applications on the newly active SRP module are restarted. Each application
reconstructs itself from the mirrored data, restoring its state and configuration as it was
before the switchover. Forwarding through the fabric is interrupted for about 1 second
on the E120 and E320 routers and about 4 seconds on the ERX1440 router.
The SRP switchover restarts the routing protocols and triggers a graceful restart because
the routes need to be recomputed. This recalculation can take up to 90 seconds. Data
continues to be forwarded through routes that were learned before the upgrade of the
line module control planes.

Line Module Forwarding Plane Upgrade

While the applications on the SRP module and the line modules reconstruct themselves,
they also begin to build up the new state for the forwarding subsystem. All applications
on the line module signal the system when they are ready to start the forwarding upgrade.
Because upgrading the forwarding plane affects forwarding through the chassis for up
to 30 seconds on the E120 and E320 routers and about 50 seconds on the ERX1440
router, unified ISSU does not proceed until the routing protocols have signaled that route
reconvergence has completed. Unified ISSU then instructs all line modules to
simultaneously upgrade their forwarding subsystems.
The line modules then perform the following steps:
Halt forwarding through the line modules. Although any links to external devices
1.
remain up, incoming data is dropped.
Update any changed programmable hardware devices.
2.
Update the forwarding subsystem with the new release and upgraded configuration
3.
data.
Update the routing tables with the reconverged routes.
4.
Resume forwarding.
5.
Unified ISSU Phases Overview on page 107
Halt of Unified ISSU During Upgrade Phase Overview on page 143
Halting Unified ISSU During Upgrade Phase on page 143
issu start
show issu
halt
reload
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