Junos Help: On the Router?
Did you know you can get all the help you need right on a Juniper router? It’s true! This shouldn’t be especially surprising, when you consider the FreeBSD roots. Let’s take a quick look at the options available.Obviously the first thing we do is log into the router. If you are logging in as root, enter the Junos cli using the “cli” command. From there, we can check out the options under “help ?”:
cjones@R2> help ? Possible completions: <[Enter]> Execute this command apropos Find help information about a topic reference Reference material syslog System log error messages tip Tip for the day topic Help for high level topics | Pipe through a command
Let’s start with tip, because it’s simple and fun. With this command you simply type “help tip cli” and you’re given a randon Junos tip:
cjones@R2> help tip cli JUNOS tip: Use the 'apply-path' statement to define a prefix list containing prefixes extracted from any configuration path.
Woo!
Okay, so now that we’re done playing around, we’ll get into the meat of the subject. First we’ll look at the “apropos” option. With this, we will see a list of commands that include the subject you enter. For example:
cjones@R2> help apropos ? Possible completions:Help topic, regular expression, or command cjones@R2> help apropos neighbor | match ospf clear ospf neighbor Clear OSPF neighbors clear ospf neighbor clear ospf3 neighbor Clear OSPFv3 neighbors clear ospf3 neighbor Name of OSPFv3 neighbor show ospf neighbor Show OSPF neighbor status information show ospf neighbor show ospf backup neighbor Show OSPF backup neighbors show ospf3 neighbor Show OSPFv3 neighbor status show ospf3 neighbor show ospf3 backup neighbor Show OSPFv3 backup neighbors help topic ospf neighbor help topic ospf dead-interval help topic ospf3 dead-interval help reference ospf neighbor help reference ospf no-neighbor-down-notification Don't signal RSVP about down OSPF neighbors help reference ospf dead-interval help reference ospf3 neighbor help reference ospf3 dead-interval
Notice that we used the pipe with the “match” function to only include the lines that match “ospf”. Very helpful indeed if you need to remember command syntax or a show command!
Next on our list is “reference“. This command allows us to read the Juniper documentation on a topic. In our example, we’ll look up information in the Juniper documentation about the OSPF metric command:
cjones@R2> help reference ospf metric
metric
Syntax
metric metric;
Hierarchy Level
[edit logical-systems logical-system-name protocols (ospf | ospf3) area
area-id interface interface-name],
[edit logical-systems logical-system-name protocols ospf area area-id
interface interface-name topology (ipv4-multicast | name)],
[edit logical-systems logical-system-name protocols ospf3 realm
(ipv4-unicast | ipv4-multicast | ipv6-multicast) area area-id interface
interface-name],
[edit logical-systems logical-system-name routing-instances
routing-instance-name protocols (ospf | ospf3) area area-id interface
interface-name],
[edit logical-systems logical-system-name routing-instances
routing-instance-name protocols ospf area area-id sham-link-remote],
[edit logical-systems logical-system-name routing-instances
routing-instance-name protocols ospf area area-id interface
interface-name topology (ipv4-multicast | name)],
[edit logical-systems logical-system-name routing-instances
routing-instance-name protocols ospf3 realm (ipv4-unicast |
ipv4-multicast | ipv6-multicast) area area-id interface interface-name],
[edit protocols (ospf | ospf3) area area-id interface interface-name],
[edit protocols ospf area area-id interface interface-name topology
(ipv4-multicast | name)],
[edit protocols ospf3 realm (ipv4-unicast | ipv4-multicast |
ipv6-multicast) area area-id interface interface-name],
[edit routing-instances routing-instance-name protocols (ospf | ospf3)
area area-id interface interface-name],
[edit routing-instances routing-instance-name protocols ospf area
area-id sham-link-remote],
[edit routing-instances routing-instance-name protocols ospf area
area-id interface interface-name topology (ipv4-multicast | name)],
[edit routing-instances routing-instance-name protocols ospf3 realm
(ipv4-unicast | ipv4-multicast | ipv6-multicast) area area-id interface
interface-name]
Release Information
Statement introduced before Junos OS Release 7.4.
Statement introduced in Junos OS Release 9.0 for EX Series switches.
Support for Multitopology Routing introduced in Junos OS Release 9.0.
Support for Multitopology Routing introduced in Junos OS Release 9.0 for
EX Series switches.
Support for the realm statement introduced in Junos OS Release 9.2.
Support for the realm statement introduced in Junos OS Release 9.2 for
EX Series switches.
Description
Specify the cost of an OSPF interface. The cost is a routing metric that
is used in the link-state calculation.
To set the cost of routes exported into OSPF, configure the appropriate
routing policy.
Options
metric-Cost of the route.
Range: 1 through 65,535
Default: By default, the cost of an OSPF route is calculated by
dividing the reference-bandwidth value by the bandwidth of the physical
interface. Any specific value you configure for the metric overrides the
default behavior of using the reference-bandwidth value to calculate the
cost of route for that interface.
Required Privilege Level
routing-To view this statement in the configuration.
routing-control-To add this statement to the configuration.
Related-Topics
* bandwidth-based-metrics
* reference-bandwidth
* Configuring the Metric Value for OSPF Interfaces
* Configuring OSPF Sham Links
* Configuring Multitopology Routing in OSPF
You can see how useful this could potentially be! Next up is “syslog“. This option gives an explanation of every single syslog event type:
cjones@R2> help syslog ? Possible completions: <[Enter]> Execute this commandSystem log tag or regular expression ACCT_ACCOUNTING_FERROR LOG_PFE,Error occurred during file processing ACCT_ACCOUNTING_FOPEN_ERROR LOG_PFE,Open operation failed on file ACCT_ACCOUNTING_SMALL_FILE_SIZE LOG_PFE,Maximum file size is smaller than record size ACCT_BAD_RECORD_FORMAT LOG_PFE,Record format does not match accounting profile ACCT_CU_RTSLIB_ERROR LOG_PFE,Error occurred obtaining current class usage statistics ACCT_FORK_ERR LOG_PFE,Could not create child process ACCT_FORK_LIMIT_EXCEEDED LOG_PFE,Could not create child process because of limit ACCT_GETHOSTNAME_ERROR LOG_PFE,gethostname function failed ACCT_MALLOC_FAILURE LOG_PFE,Memory allocation failed ACCT_UNDEFINED_COUNTER_NAME ANY,Filter profile used undefined counter name ACCT_XFER_FAILED LOG_PFE,Attempt to transfer file failed ACCT_XFER_POPEN_FAIL LOG_PFE,File transfer failed ALARMD_CONFIG_ACCESS_ERROR LOG_DAEMON,Alarmd could not parse configuration database ALARMD_CONFIG_CLOSE_ERROR LOG_DAEMON,Closing of configuration database failed ALARMD_CONFIG_PARSE_ERROR LOG_DAEMON,Parsing of configuration failed ALARMD_CONFIG_RECONFIG_ERROR LOG_DAEMON,Reconfiguration failed ALARMD_CONNECTION_FAILURE LOG_DAEMON,Alarmd connection to another process failed ALARMD_DECODE_ALARM_OBJECT_ERROR LOG_DAEMON,Decoding of the alarm object failed ALARMD_EXISTS LOG_DAEMON,Another alarmd was already running ALARMD_EXISTS_TERM_OTHER LOG_DAEMON,Alarmd terminated an existing alarmd and exited ALARMD_IFDALARM_TYPE_ERROR LOG_DAEMON,Alarmd could not recongnize IFD alarm type ... WEB_PIDFILE_LOCK LOG_DAEMON,httpd-gk could not lock PID file WEB_PIDFILE_UPDATE LOG_DAEMON,httpd-gk could not update PID file WEB_UNAME_FAILED LOG_DAEMON,httpd-gk could not retrieve hostname WEB_WEBAUTH_AUTH_FAIL LOG_DAEMON,web-authentication authentication failed WEB_WEBAUTH_AUTH_OK LOG_DAEMON,web-authentication authentication success WEB_WEBAUTH_CONNECT_FAIL LOG_DAEMON,web-authentication socket connect failed facility System facility messages | Pipe through a command
Here’s some example output:
cjones@R2> help syslog ALARMD_EXISTS
Name: ALARMD_EXISTS
Message: alarmd already running; exiting
Help: Another alarmd was already running
Description: The alarm process (alarmd) exited because it discovered that another alarmd
process was already running.
Type: Event: This message reports an event, not an error
Severity: error
Facility: LOG_DAEMON
Nice to not have to Google this stuff, huh?
Finally, we’ll wrap up with the “topic” help option. This command will give you a full text description of the topic you select. Again, we’ll stick to OSPF metrics:
cjones@R2> help topic ospf metric
Configuring the Metric Value for OSPF Interfaces
All OSPF interfaces have a cost, which is a routing metric that is used in
the link-state calculation. Routes with lower total path metrics are
preferred over those with higher path metrics.
When several equal-cost routes to a destination exist, traffic is
distributed equally among them.
The cost of a route is described by a single dimensionless metric that is
determined using the following formula:
cost = reference-bandwidth / bandwidth
You can modify the reference-bandwidth value. The bandwidth value refers
to the actual bandwidth of the physical interface.
You can override the default behavior of using the reference bandwidth to
calculate the metric cost of a route by configuring a specific metric
value for any OSPF interface.
To modify the reference bandwidth, include the reference-bandwidth
statement:
reference-bandwidth reference-bandwidth;
For a list of hierarchy levels at which you can include these statements,
see the statement summary sections for these statements.
The default value of the reference bandwidth is 100 Mbps (which you
specify as 100,000,000), which gives a metric of 1 for any interface with
a physical bandwidth that is 100 Mbps or greater. For reference-bandwidth,
you can configure a value from 9600 through 1,000,000,000,000 bits.
For example, if you set the reference bandwidth to 1 Gbps (that is,
reference-bandwidth is set to 1,000,000,000), a 100-Mbps interface has a
default metric of 10.
By default, the loopback interface (lo0) metric is 0. No bandwidth is
associated with the loopback interface.
When you specify a metric for a specific OSPF interface, that value is
used to determine the cost of routes advertised from that interface. To
specify a metric for routes advertised from an interface, include the
metric statement:
area area-id {
interface interface-name {
metric metric;
}
}
For metric, you can specify a value from 1 through 65,535.
Related-Topics
As you can see, the help system in Junos is fantastic and exceptionally well detailed. It’s also current, as it comes as part of the Junos install package for each release. It can also come in very handy during a JNCIE lab exam, where you’re starved for time!
Oh, I can’t help but include this here too, even though it’s not actually part of the help system. Junos has a hidden command that spits out bad poetry. No, really.
cjones@R2> show version and haiku
Hostname: R2
Model: srx210h
JUNOS Software Release [10.4R3.4]
TTL down one
the end nearer with each hop
little packet, poof.
Yeah… you can have some fun with that one :)
Excellent post – this was something I was just checking out the other day. Keep em’ coming!