56 AT-8800 Series Switch User Guide
Software Release 2.6.1
C613-02039-00 REV A
Upgrading Switch Software
When you first start the switch, it automatically loads the software release from
FLASH memory into RAM, where the CPU uses it to run all the router’s
software features. The switch may also load a patch file to improve the main
release. The software release and any patch files are current when the switch is
produced at the factory.
When Allied Telesyn makes a new patch or release available, you may want to
upgrade the software on your switch to use a new patch or release file. You can
download the latest software patches, full software releases, and CLI help files
from the support site at: http://www.alliedtelesyn.co.nz/support/ar400.
Make sure you download a patch or release file that matches your switch
model. A patch or release file for AT-8800 Series Switch has 86 as the first two
digits of the filename. Patch files have the file extension .paz and release files
have the file extension .rez. For example, the Software Release 2.6.1 for the
AR450S has the filename 86s-261.rez.
Release and patch files are compressed ASCII files, and consist of a header
followed by a sequence of Motorola S-records containing the actual code for
the release or patch. The header has a standard format, which provides
information about the release or patch to the switch.
Do not change the header in a release or patch file. At best, this will cause the
file load or install to fail, at worst the switch could be put into a state where it
will not boot correctly until field service action is taken.
The current release and patch file are set as the preferred install. The switch
also has a very limited version of the software stored in a specific part of
FLASH (the FLASH boot block). You cannot delete this version as it is the
defau lt, or b oot in stall . When you lo ad a ne w soft ware rel ease o r patc h, you can
set it to run once, the next time the switch reboots. This temporary install
allows you to test run a new release or patch once, before you make it the
preferred install. If the temporary install fails the switch will automatically run
the preferred install if there is one, or otherwise the default install, the next
time the switch reboots.
When the switch reboots, it checks the install information in a strict order:
• Firstly, the switch checks the temporary install. If a temporary install is
specified, the switch loads it into RAM and runs it. At the same time, it
deletes the temporary install information so it will not load a second
time. This information is deleted even if the temporary install triggers a
fatal condition causing the switch to reboot immediately.
• Secondly, if no temporary install is defined, or the install information is
invalid, the switch checks the preferred install. If present, this install is
loaded. The switch never deletes the preferred install information.
• Thirdly, if neither a temporary install nor a preferred install is specified,
the switch loads the default install. The default install is always present
in the switch because if, for some reason, it is not, the INSTALL module
will restore it.
The preferred install should not be set up with an untested release or patch. It
is advisable to install new releases or patches as the temporary install, and