Specifications

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Operators can configure the M20/M40 by entering configuration mode and
creating a hierarchy of configuration statements. A configuration can be created
on the router, interactively, by using the CLI or by loading a text (ASCII) file
containing the statement hierarchy that was created earlier. All properties of the
JUNOS software can be configured, including: interfaces, general routing
information, routing protocols, user access, as well as a number of hardware
properties.
Once changes are made, the candidate configuration (or piece of the
configuration) can be “committed” to become the running configuration. A syntax
check is automatically run when a commit is executed. If the committed
configuration appears unstable, then a “rollback” command allows users to
replace the running config with one of the last eight previous running
configurations.
Operators may also run non-destructive simulations with some of the more
complex portions of system configuration. For example, a new routing policy can
be tried out to determine what the operational effect will be before actually
activating the policy.
Additionally, the JUNOS software supports partitioned operator access
permission levels. Users can define access levels for UI commands and then
assign each operator to a specific level. A change history tracks the changes
made by a particular operator.
To reduce the risk associated with complex policy configuration, the JUNOS
software supports an off-line policy test tool, which allows operators to ensure
that policy filters are set correctly before implementing them.
The JUNOS also offers command completion functionality.
The configuration file in JUNOS is stored in ASCII text format.
5.1.3 Telnet access
Telnet as well as ssh access is available for management functions. You can
configure the connection-limit for the maximum number of established sessions,
from 1 through 250. Default is 75.
5.1.4 Documentation and On-line (Long Help) Documentation
Software and Hardware manuals are provided via hardcopy. They are also
available on CD and via the web. Additionally, technical notes, FAQs, and
solutions are located under the support website.
Using the CLI, and extended “help” command hierarchy provides detailed help,
using the “help topic” and “help summary” commands. These commands provide
what might be described as “long help”. They link to files on the router’s hard
disk.
5.2 Software Download
The JUNOS software can be reinstalled using the LS120 floppy drive on the M40
and the PC Flash card on the M20. It can also be reinstalled over the network
using SCP, FTP or HTTP. The download can be in-band or out-of-band. The
router doesn’t need to be taken down during download except that the routing
daemons restart upon reinstalling the jroute (routing protocol software) package
on the router.
5.3 Software Startup and emergency recovery procedures
Normally, the router boots from the flash disk. If it fails, it attempts to boot from
the hard drive, which is the alternate medium.
If a removable medium is installed when the router boots, the router attempts to
boot the image on it. If the router fails, it next tries the flash disk and finally the
hard disk.
In cases where it cannot boot from the flash or hard drive, you can boot it from
the removable boot media (LS120 or PC Flash drive).
The following procedure describes how to reinstall the JUNOS software from the
removable media:
§ Insert the removable medium into the router.