Specifications

ISSU Introduction
New and Enhanced Features in AlliedWare Plus 5.4.4 Major and Minor Versions 85
ISSU Operation
During the ISSU process, each CFC within either the chassis, or VCS Plus stack, is
sequentially rebooted. For this process, ISSU sets the boot system configuration to boot
using the release being upgraded to. When the stack is then rebooted, the CFCs start with
the newly applied release.
Initially, ISSU gathers information about each of the CFC nodes within the stack. It uses
this information to record which CFCs have been upgraded and which are yet to be
upgraded. ISSU then processes this information in node ID order, starting with the CFC
that has the highest node ID and ending with the CFC that has the lowest. Once a node
has finished “syncing,” the next node is rebooted. The Active CFC is left until all the CFC
nodes have been rebooted.
ISSU provides the following operating facets:
■ Designed for Allied Telesis chassis products such as the x8100 Series switch.
■ CFCs are sequentially upgraded with no network downtime and only a single fast
failover.
■ Line cards must be manually upgraded (or automatically upgraded using triggers)
once the CFC upgrade process is complete, i.e. before the next ISSU is attempted.
■ During the ISSU process, two different software releases will be running
simultaneously on the chassis.
■ Communication between cards continues while ISSU is in progress.
ISSU Phases
The ISSU process should be considered as having two phases.
1. An automatic phase, during which the CFCs are automatically upgraded.
2. A manual phase, during which the line cards are manually upgraded.
The ISSU process is only considered complete once all CFCs and line cards are running the
new software version.
Automatic Phase
This phase of ISSU begins by comparing the first three numbers of the running versions
against the version being upgraded to. For the ISSU process to successfully apply, these
three numbers must match. However, no system check is made on either the minor or
maintenance components, -x.y. Presently, ISSU can be tested by applying an upgrade from
5.4.4-1.1 to the same version, and can be applied in active operation when the move is
made from the current version 5.4.4-1.1, to the next maintenance version 5.4.4-1.2. To
what extent ISSU compatibility extends to the minor and maintenance components for
future releases and how these will apply will be documented in the release notes for each
specific build.
The software release that is configured using the boot system command must be
available for all CFCs before ISSU can begin. The release must be locally stored on flash or a
usb storage device. This release will be used (rolled back to) if there is an error in the ISSU
process.