JNCIA Refresher #1 – User Interface

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Decided to get my act in gear and get started with my journey on becoming a JNCIE engineer, Iโ€™ve worked with Junos for a couple years now (using it properly over last 12 months!), I would like to think I know a few bits about it, but when it comes to exams its always good to go over the “basics”

Before getting into it, I’ve taken a look on the Juniper JNCIA Track page to check the topics that exam takers will be expected to know:

Networking Fundamentals
Junos OS Fundamentals
User Interfaces
Junos Configuration Basics
Operational Monitoring and Maintenance
Routing Fundamentals
Routing Policy and Firewall Filters

Having a quick look over these topics, although they are pretty straightforward for me, I always been told, never time to little of a problem! With this in mind, ill be making series a posts to refresh myself in the basic understanding of Junos and Juniper devices. Although I use Junos everyday at work, I’ve said to myself doing a bit of studying will be usefu1 as:

1. I may learn something new
2. I’ll (definitely) remember something I’ve forgotten
3. Most importantly, how things work in the real world and how things are in an exam are COMPLETELY different, so exam techniques are always needed!

As I was going through the different topics, there were a few things I just looked over, as I was confident enough with! So i wont be going over thing in these posts

With that being said, let begin ๐Ÿ˜€

User Interface

CLI modes and navigation

With Junos, there are 3 different levels of access available. The prompt signs show these:

[email protected]_SRX% <------- the % prompt shows that we are on the Unix kernal level. As Junos is a based on FreeBSD the overall archietecture is Linux based, so you will be able to do a number of linux commands. You can into this Unix kernal level either by logging into your device as root or if you are in Operational mode, you will need to use the command start shell [email protected]_SRX> <------- the > prompt shows that we are on the Operational level. This is where we will be able checks (via show commands), troubleshoot and make system requests. You will enter this mode automatically if you are logged in with a created user. If you are log in as root, to get Operation mode from kernal level, you will need to run the command cli

Operational Mode Commands
Most used commands from this level would be:

[email protected]_SRX> ?      
Possible completions:
  clear                Clear information in the system
  configure            Manipulate software configuration information
  file                 Perform file operations
  help                 Provide help information
  load                 Load information from file
  monitor              Show real-time debugging information
  mtrace               Trace multicast path from source to receiver
  op                   Invoke an operation script
  ping                 Ping remote target
  quit                 Exit the management session
  request              Make system-level requests
  restart              Restart software process
  save                 Save information to file
  set                  Set CLI properties, date/time, craft interface message
  show                 Show system information
  ssh                  Start secure shell on another host
  start                Start shell
  telnet               Telnet to another host
  test                 Perform diagnostic debugging
  traceroute           Trace route to remote host

[email protected]_SRX# <------- the # prompt shows we are in configuration level. This is where we can make configure changes on the device. To get the configuration, you will need to be Operational mode and you will need to either run the command configure or edit [su_spoiler title="Configuration Mode Commands" style="fancy"]Most used commands from this level:

[email protected]_SRX# ?
Possible completions:
  <[Enter]>            Execute this command
  activate             Remove the inactive tag from a statement
  annotate             Annotate the statement with a comment
  commit               Commit current set of changes
  copy                 Copy a statement
  deactivate           Add the inactive tag to a statement
  delete               Delete a data element
  edit                 Edit a sub-element
  exit                 Exit from this level
  extension            Extension operations
  help                 Provide help information
  insert               Insert a new ordered data element
  load                 Load configuration from ASCII file
  prompt               Prompt for an input
  protect              Protect the statement
  quit                 Quit from this level
  rename               Rename a statement
  replace              Replace character string in configuration
  rollback             Roll back to previous committed configuration
  run                  Run an operational-mode command
  save                 Save configuration to ASCII file
  set                  Set a parameter
  show                 Show a parameter
  status               Show users currently editing configuration
  top                  Exit to top level of configuration
  unprotect            Unprotect the statement
  up                   Exit one level of configuration
  wildcard             Wildcard operations
[/su_spoiler]

Junos is organized in a hierarchy model. When we enter configuration mode we see that we are at the top of the edit hierarchy by the [edit]

[edit]
[email protected]_SRX#

From here we are able to drill down into the different hierarchical levels and make changes that will affect that particular level. For an example, if we wanted to configure the interface ge-0/0/3 with the IP address 10.1.10.100/24. We have the ability to drill down the interface hierarchy to make the change, we will use the ‘edit’ command to change levels . It is important to know as well, the different hierarchical levels will have specific commands exclusive for that particular hierarchical level

Top levelInterface levelPhysical Port level
[email protected]_SRX# edit ?
Possible completions:
> access               Network access configuration
> access-profile       Access profile for this instance
> accounting-options   Accounting data configuration
> applications         Define applications by protocol characteristics
> bridge-domains       Bridge domain configuration
> chassis              Chassis configuration
> class-of-service     Class-of-service configuration
> ethernet-switching-options  Ethernet-switching configuration options
> event-options        Event processing configuration
> firewall             Define a firewall configuration
> forwarding-options   Configure options to control packet forwarding
> groups               Configuration groups
> interfaces           Interface configuration
> multi-chassis        
> policy-options       Policy option configuration
> protocols            Routing protocol configuration
> routing-instances    Routing instance configuration
> routing-options      Protocol-independent routing option configuration
> schedulers           Security scheduler
> security             Security configuration
> services             Set services parameters
> smtp                 Simple Mail Transfer Protocol service configuration
> snmp                 Simple Network Management Protocol configuration
> switch-options       Options for default routing-instance of type virtual-switch
> system               System parameters
> vlans                VLAN configuration
> wlan                 Wireless access point configuration
[edit interfaces]
[email protected]_SRX# set ?
Possible completions:
       Interface name
+ apply-groups         Groups from which to inherit configuration data
+ apply-groups-except  Don't inherit configuration data from these groups
  ge-0/0/0             Interface name
  ge-0/0/3             Test
  ge-0/0/6             Interface name
> interface-range      Interface ranges configuration
> interface-set        Logical interface set configuration
> traceoptions         Interface trace options
[edit interfaces ge-0/0/3]
[email protected]_SRX# set ?
Possible completions:
  accounting-profile   Accounting profile name
+ apply-groups         Groups from which to inherit configuration data
+ apply-groups-except  Don't inherit configuration data from these groups
  description          Text description of interface
  disable              Disable this interface
  encapsulation        Physical link-layer encapsulation
  flexible-vlan-tagging  Support for no tagging, or single and double 802.1q VLAN tagging
> gigether-options     Gigabit Ethernet interface-specific options
  gratuitous-arp-reply  Enable gratuitous ARP reply
> hold-time            Hold time for link up and link down
  link-mode            Link operational mode
  mac                  Hardware MAC address
  mtu                  Maximum transmit packet size (256..9192)
  native-vlan-id       Virtual LAN identifier for untagged frames (0..4094)
  no-gratuitous-arp-reply  Don't enable gratuitous ARP reply
  no-gratuitous-arp-request  Ignore gratuitous ARP request
  no-per-unit-scheduler  Don't enable subunit queuing on Frame Relay or VLAN IQ interface
  no-traps             Don't enable SNMP notifications on state changes
  passive-monitor-mode  Use interface to tap packets from another router
  per-unit-scheduler   Enable subunit queuing on Frame Relay or VLAN IQ interface
  promiscuous-mode     Enable promiscuous mode for L3 interface
  speed                Link speed
  stacked-vlan-tagging  Stacked 802.1q VLAN tagging support
> switch-options       Front end ports configuration
> traceoptions         Interface trace options
  traps                Enable SNMP notifications on state changes
> unit                 Logical interface
  vlan-tagging         802.1q VLAN tagging support
With hierarchical levels you have the option of either drilling down to the bottom of the hierarchy to make change or you can 'set' the full command from the top or any hierarchical level.
Command SET within interface hierarchy levelCommand SET from top level
[edit interfaces ge-0/0/3]
[email protected]_SRX# set unit 0 family inet address 10.1.100.100/24
[edit]
[email protected]_SRX# set interface ge-0/0/3 unit 0 family inet address 10.1.100.100/24
Hierarchy Commands

edit = Moves you down to the level you need
up = Moves you one level up from the current hierarchical level
top = Moves you to the top of the configuration hierarchy

CLI Help

One very useful (that I just learnt myself!) is the help command. This command shows you the inbuilt documentation that is on all juniper devices. The command that will be most likely used the reference, apropos and topic.

[email protected]_SRX# 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

The topic option will give you detail, description and context about particular topic on the device

Help Topic Example
[email protected]_SRX# help topic interfaces address   
                       Configuring the Interface Address

   You assign an address to an interface by specifying the address when
   configuring the protocol family. For the inet or inet6 family, configure
   the interface IP address. For the iso family, configure one or more
   addresses for the loopback interface. For the ccc, ethernet-switching,
   tcc, mpls, tnp, and vpls families, you never configure an address.

   +------------------------------------------------------------------------+
   |       | The point-to-point (PPP) address is taken from the loopback    |
   | Note: | interface address that has the primary attribute. When the     |
   |       | loopback interface is configured as an unnumbered interface,   |
   |       | it takes the primary address from the donor interface.         |
   +------------------------------------------------------------------------+

   To assign an address to an interface, include the address statement:
     address address {
         broadcast address;
         destination address;
         destination-profile name;
         eui-64;
         preferred;
         primary;
     }
   You can include these statements at the following hierarchy levels:
     * [edit interfaces interface-name unit logical-unit-number family
       family]
     * [edit logical-systems logical-system-name interfaces interface-name
       unit logical-unit-number family family]
   In the address statement, specify the network address of the interface.
   For each address, you can optionally configure one or more of the
   following:
     * Broadcast address for the interface subnet-Specify this in the
       broadcast statement; this applies only to Ethernet interfaces, such as
       the management interface fxp0, em0, or me0 the Fast Ethernet
       interface, and the Gigabit Ethernet interface.
     * Address of the remote side of the connection (for point-to-point
       interfaces only)-Specify this in the destination statement.
     * PPP properties to the remote end-Specify this in the
       destination-profile statement. You define the profile at the [edit
       access group-profile name ppp] hierarchy level (for point-to-point
       interfaces only).
     * Whether the router or switch automatically generates the host number
       portion of interface addresses-The eui-64 statement applies only to
       interfaces that carry IPv6 traffic, in which the prefix length of the
       address is 64 bits or less, and the low-order 64 bits of the address
       are zero. This option does not apply to the loopback interface (lo0)
       because IPv6 addresses configured on the loopback interface must have
       a 128-bit prefix length.

       +-------------------------------------------------------------+
       | Note: | IPv6 is not currently supported for the QFX Series. |
       +-------------------------------------------------------------+

     * Whether this address is the preferred address-Each subnet on an
       interface has a preferred local address. If you configure more than
       one address on the same subnet, the preferred local address is chosen
       by default as the source address when you originate packets to
       destinations on the subnet.

       By default, the preferred address is the lowest-numbered address on
       the subnet. To override the default and explicitly configure the
       preferred address, include the preferred statement when configuring
       the address.
                                        
     * Whether this address is the primary address-Each interface has a
       primary local address. If an interface has more than one address, the
       primary local address is used by default as the source address when
       you send packets from an interface where the destination provides no
       information about the subnet (for example, some ping commands).
   By default, the primary address on an interface is the lowest-numbered
   non-127 (in other words, non-loopback) preferred address on the interface.
   To override the default and explicitly configure the preferred address,
   include the primary statement when configuring the address.
     * Configuring Interface IPv4 Addresses
     * Configuring Interface IPv6 Addresses

  Related-Topics

        * Configuring IPCP Options
        * Configuring Default, Primary, and Preferred Addresses and
          Interfaces

The Reference option is command structure, it is a type of configuration assistances. As it provides all the possible configuration syntax thatโ€™s available for that topic

Help Reference Example
[email protected]_SRX# help reference interfaces address 
address

  Syntax

     address address {
         arp ip-address (mac | multicast-mac) mac-address ;
         broadcast address;
         destination address;
         destination-profile name;
         eui-64;
         master-only;
         multipoint-destination address dlci dlci-identifier;
         multipoint-destination address {
             epd-threshold cells;
             inverse-arp;
             oam-liveness {
                 up-count cells;
                 down-count cells;
             }
             oam-period (disable | seconds);
             shaping {
                 (cbr rate | rtvbr peak rate sustained rate burst length |
     vbr peak rate sustained rate burst length);
                 queue-length number;
             }
             vci vpi-identifier.vci-identifier;
         }
         primary;
         preferred;
         (vrrp-group | vrrp-inet6-group) group-number {
             (accept-data | no-accept-data);
             advertise-interval seconds;
             authentication-type authentication;
             authentication-key key;
             fast-interval milliseconds;
             (preempt | no-preempt) {
                 hold-time seconds;
             }
             priority-number number;
             track {
                 priority-cost seconds;
                 priority-hold-time interface-name {
                     interface priority;
                     bandwidth-threshold bits-per-second {
                         priority;
                     }
                 }
                 route ip-address/mask routing-instance instance-name
     priority-cost cost;
             }
             virtual-address [ addresses ];
         }
     }

  Hierarchy Level

     [edit interfaces interface-name unit logical-unit-number family family],
     [edit logical-systems logical-system-name interfaces interface-name unit
     logical-unit-number family family]

  Release Information

     Statement introduced before Junos OS Release 7.4.
     Statement introduced in Junos OS Release 9.0 for EX Series switches.
     Statement introduced in Junos OS Release 11.1 for QFX Series switches.

  Description

     Configure the interface address.

     +----------------------------------------------------------------------+
     | Note: | The vrrp High Availability functionality is not available    |
     |       | for the QFX Series switches                                  |
     +----------------------------------------------------------------------+

  Options

     address-Address of the interface.

     The remaining statements are explained separately.

     +----------------------------------------------------------------------+
     | Note: | The edit logical-systems hierarchy is not available on       |
     |       | QFabric switches.                                            |
     +----------------------------------------------------------------------+

  Required Privilege Level

     interface-To view this statement in the configuration.
     interface-control-To add this statement to the configuration.

  Related-Topics

        * Configuring the Protocol Family
        * negotiate-address
        * unnumbered-address (Ethernet)
        * Junos OS System Basics Configuration Guide

The Apropos option gives you all the commands that have particular word you are looking for. This will include clear, show and help commands if in Operational Mode and the set commands if you're in Configuration Mode.

Help Apropos Example
[email protected]_SRX# help apropos lldp  
set logical-systems  protocols lldp 
    Link Layer Detection Protocol
set logical-systems  protocols lldp disable 
    Disable LLDP
set logical-systems  protocols lldp traceoptions 
    Trace options for LLDP
set logical-systems  protocols lldp management-address  
    LLDP management address
set logical-systems  protocols lldp advertisement-interval  
    Transmit interval for LLDP messages
set logical-systems  protocols lldp transmit-delay  
    Transmit delay time interval for LLDP messages
set logical-systems  protocols lldp hold-multiplier  
    Hold timer interval for LLDP messages
set logical-systems  protocols lldp lldp-configuration-notification-interval  
    Time interval for LLDP notification
set logical-systems  protocols lldp interface disable 
    Disable LLDP
set logical-systems  protocols lldp-med 
    LLDP Media Endpoint Discovery
set logical-systems  protocols lldp-med disable 
    Disable LLDP
set logical-systems  protocols lldp-med interface disable 
    Disable LLDP
set logical-systems  protocols dot1x authenticator interface lldp-med-bypass 
    Bypass dot1x authentication, use lldp-med based authentication
set protocols lldp 
    Link Layer Detection Protocol
set protocols lldp disable 
    Disable LLDP
set protocols lldp traceoptions 
    Trace options for LLDP
set protocols lldp management-address  
    LLDP management address
set protocols lldp advertisement-interval  
    Transmit interval for LLDP messages
set protocols lldp transmit-delay  
    Transmit delay time interval for LLDP messages
set protocols lldp hold-multiplier  
    Hold timer interval for LLDP messages
set protocols lldp lldp-configuration-notification-interval  
    Time interval for LLDP notification
set protocols lldp interface disable 
    Disable LLDP
set protocols lldp-med 
    LLDP Media Endpoint Discovery
set protocols lldp-med disable 
    Disable LLDP
set protocols lldp-med interface disable 
    Disable LLDP
set protocols dot1x authenticator interface lldp-med-bypass 
    Bypass dot1x authentication, use lldp-med based authentication
set vlans  dot1q-tunneling layer2-protocol-tunneling lldp 
    Tunnel LLDP PDUs

Keyboard shortcuts are useful to know as you will be able to get configure command quicker and have less time looking at the screen (which is always nice :D)

Keyboard Commands
ctrl + b = moves the cursor one to the left (backward)
ctrl + f = moves the cursor one to the right (forward)
ctrl + a = moves the cursor to the beginning of the line
ctrl + e = moves the cursor to the end of the line
ctrl + d = deletes the character that the cursor is on
ctrl + w = deletes the word left of the cursor
ctrl + k = deletes everything on the right of the cursor
ctrl + u = deletes the whole line
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Keeran Marquis

Network Engineer
Keeran Marquis is a Network Engineer. His main goal is to learn everything within the Networking field, pick up a little bit of scripting, be a poor man sysadmin and share whatever he knows! All Posts are his own views, opinions and experiences, no guarantees they will work for you but point you in the right direction ๐Ÿ™‚
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