This is how we roll(back)!

In this session of my Juniper blog, we will be talking about syntax checking, the rollback command, and what to do when you need help from your Juniper router. Remember that a Juniper router has two configurations at all times, the active configuration and the candidate configuration. When you commit a configuration, the candidate configuration becomes the active configuration.

The old active configuration is archived into a rollback file, rollback 1. Juniper routers save 49 previous configurations.

• You must commit the rollback file to make it active



• rollback 0 will copy the active config to the candidate config



• You can use the compare command to compare any two files and output the lines that are different




• Eg: user@routername# show compare under the [edit] hierarchy

"Don't worry I will save you!"

Many times a user may wish to save the candidate configuration to his/her home directory. You can use a pipe command to do this:

• Eg: user@routername# show configuration save

Caution! The save command saves from the current hierarchy you are in! If you were in another hierarchy, you could issue the top command to go to [edit] Then issue the save command from there in order to save the whole configuration. under the [edit] hierarchy it would look like:

Eg: user@routername# save we_love_junos

Suppose you have the same system login information you want configured for a number of routers in your enterprise. In this scenario it is desirable to save a portion of the configuration. Remember that the save command saves from the current hierarchy. In the case of our router access, its' information is contained in the [edit system login] hierarchy

• Eg: user@routername# save only_system_logins

Now that we can save part or the whole active configuration, we may also wish to archive a section of a configuration in whole or in part. We do this with the set archival configuration commands. You can archive on commit or at a time you specify.

Acronyms of the Moment:

FTP: File Transfer Protocol

SCP: Secure CoPy

FTP and SCP can be used to copy the archival files from the router to a server under archival-sites configuration.

"Load 'em up and move out!"

Loading a configuration is accomplished with the load command. The load command has several options. Only a few are covered here:

• load override replaces current candidate config with file you specify



• Eg: user@routername# load override we_love_junos

You can use load merge to add small sections of configuration to the candidate config.

• Eg: user@routername# load merge only_system_logins



• Alternately, the load terminal command can be used to paste in configuration. In using this method you must be in the hierarchy level the configuration you are pasting in lives. You can use the relative keyword in the [edit system] hierarchy to paste in our router login config.



• You may load set commands directly into the router with load set terminal

"Asking our router for help."

• The (?) mark


• help command


• help topic


• help reference

help topic and help reference have some differences. help reference will show actual syntax and usage, whereas help topic will tell you what a command does and when to use it.

Ancillary things:

• schedule configuration activation with the commit at timeinterval command



• removing large pieces of configuration using wildcard delete string command



• common configuration changes can be made with the replace pattern pattern command

Exam Topics Check-In

• list line of enterprise routers


• describe transit and host processing


• packet flow differences between M7i/M10 and J-Series routers


• key differences between the M7i/M10 and J-Series routers


• configuration management


• JUNOS CLI features (modes, prompts, auto-complete, EMACS keystrokes, and pipe


• commands used in configuration mode (edit, set, delete, and commit)


• manipulation of saved configuration files (rollback and load, and rollback file locations)


• describe the configuration hierarchy


• describe active, candidate, and rollback configurations