Requirement
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Overview
Even in the era of zero touch configuration where everything can be modelled by YANG and automated by Ansible, CLI configuration mode is essential and will take a special important place into network engineers' heart.
Any network engineer in the room who never issued this command ?
conf t ...
Article objective
In this article, we will present you freeRouter available configuration mode. This is an essential article as it will help you in your potential daily operation task.
Diagram
[ #001 ] - "configure <mode>"
"configure viewer" is a very interesting mode as it gives you the possibility to review the router configuration from a viewer inspired from "mcedit" (Norton Midnight Commander)
r1#configure viewer ...
Then you'll be able to read your configuration from a READ-ONLY text buffer:
As a side note, you can benefit from online help by pressing <f1>
But what if I just want to view a specific object ? Let's find out how to check ONLY BGP configuration @ home:
r1#configure viewer bgp4 ...
So in this case It'll just throw my IPv4 bgp config snippet onto the viewer buffer
Same if I want to only view all interface sdn<x> from the router config:
r1#configure viewer sdn ...
This is so cool, isn't ?
Note
In big TELCO Service Provider environment, most of the time you have Technical Project Manager that just need to perform some checks related to specific customer VPN deployment. So some times, I received some calls: "Can you please that from customer the HUB site prefix 1.2.3.0/24 is configured and advertised into BGP for customer ABC in VRF YXZ ?" With "configure viewer <object>", the TPM can just check it for himself without bothering you at all ! And this without the fear to alter router configuration by accident.
PS: For that you'll need to create a aaa security config with:
- proper router aaa security policy with privilege level 1
- with or without TACACS/RADIUS authentication / authorisation and accounting
- and apply it to a specific OOBM SSH/telnet server in a specific VRF,
but this is not in the scope of the the present article and it will be the object of further articles.
In SP environment, you should not be surprised to see router configuration that has 100k lines or even more. In these environment, I've seen config with countless amount of VRF, NAT, DLSW, GRE, IPSEC tunnels, BGP peers ... "config viewer" is a great tools when you want to verify a specific stanza on a per customer or object basis and in bonus without any risk the Provider Edge router configuration.
"configure viewer" gives you the possibility to view the config or some parts of the config in read-only mode. "configure editor" gives you simply the possibility to edit also the specific running-config config stanza.
r1#configure editor ...
Then you'll be able to edit your configuration from a READ-WRITE text buffer:
As a side note, you can benefit from online help by pressing <f1>
You can press Ctrl+q in order to exit the editor. As you did not change anything it will exit the editor.
But what if I just want to edit a specific object ? Let's find out how to check ONLY BGP configuration @ home:
r1#configure editor bgp4 ...
So in this case I'll just throw my IPv4 bgp config onto the editor buffer
In this buffer let's just create a description for BGP neighbor 172.23.215.177.
Now just press Ctrl-q (as per the online help accessible using <f1>). However, freeRouter detect the buffer changed has we added BGP description configuration. Therefore it will ask you if you want to save the buffer change into the running-config and apply it.
At that moment you'll be displayed a small recap of what has been applied.
Even more cool no ?
Warning
Even if "config editor" is seducing and seems more appealing especially for beginners. This is absolutely not the case. "configure editor" mode is meant for advanced users who knows freeRouter CLI by heart. Why, you might say ? Just try to edit a gigantic BGP configuration without any contextual help just by writing a textual file and you'll understand the risk behind using "config editor". Therefore it is no recommend to use it against complex control plane object.
Please take note that "config editor" alter the running-configuration directly when you saved the editor buffer !
Note
So what's the point of having this cool feature ? This feature is powerful when it comes to simple control plane object or big repetitive object. This is very practical to use this feature against: ACL / Prefix-List / Route Policy Object / Route Map etc.
- ACL
- prefix-list
- route policy list
- route-map
but nothing to prevent you to edit BGP stanza if you feel that your freeRouter-fu needs to be challenged 
Same as "config editor", but instead of working against the running-config you are editing the startup-config. Which is more safe ... till the next reload
r1#configure startup ...
"configure reload" as its name implies is not about reloading a router whatsoever 
r1#configure reload ? <url> - source url r1#configure reload ...
This command take a <url> as argument. Basically it will fetch router configuration from the specified <url> and load it into the startup-config. It is an equivalent to Cisco "copy <url> start". From that point:
- it is up to the network operator to check the startup configuration
- and issue a reload warm in order to restart the router and test that connectivity is resuming as expected
- Check the running-config is aligned to startup-config
Warning
(repetition is not harmful) As said before "configure reload" does not reload the router. It just load the config from specified <url> into the startup-configuration. And this steps precedes a reload that has to be triggered manually by the operator after having checked the config.
Note
in day to day operation, startup-config is usually not altered directly. In TELCO SP environment, IIRC, I used it mainly to retrieve configuration from a CMDB server during 2 situations:
- Router first time installation after basic configuration staging enabling minimum connectivity
- Router hardware replacement
Note that in SP environment, as VPN owner we could handle a portfolio of customer (~10). Each customer could have ~ 2000 CPEs. You can see why "config reload" can be very handy.
"configure banner" is one of my favorite mode. It will display an editor allowing you to edit the banner of your router.
r1#configure banner ...
Press Ctrl-q and then y in order to save the banner.
Log in to you router again in order to check your new banner:
Note
in day to day operation, this banner can be written in configuration using banner encoded command
banner encoded ICAgX18gICAgICAgICAgICAgICBfX19fICAgICAgICAgICAgIF8NCiAgLyBffF8gX18gX19fICBfX198ICBfIFwgX19fICBfICAgX3wgfF8gX19fIF8gX18NCiB8IHxffCAnX18vIF8gXC8gXyBcIHxfKSAvIF8gXHwgfCB8IHwgX18vIF8gXCAnX198DQogfCAgX3wgfCB8ICBfXy8gIF9fLyAgXyA8IChfKSB8IHxffCB8IHx8ICBfXy8gfA0KIHxffCB8X3wgIFxfX198XF9fX3xffCBcX1xfX18vIFxfXyxffFxfX1xfX198X3wNCiAgXyBfXyBfX18gICBfX198IHwgX19fX18gIHwgfA0KIHwgJ19fLyBfIFwgLyBfX3wgfC8gLyBfX3wgfCB8DQogfCB8IHwgKF8pIHwgKF9ffCAgIDxcX18gXCB8X3wNCiB8X3wgIFxfX18vIFxfX198X3xcX1xfX18vIChfKQ0KDQo=
the command corresponds to the banner mentioned above.
Discussion
Most of you will simply use the basic "conf t" mode, but keep in mind that depending on your context, all the other modes are proven to be very handy. The possibility to configure 1000 router with one single config file using "config network" is a savior. Having the possibility to trigger automatic definitive router staging using "conf reload" is tremendously useful when you have to deploy 10 routers a day. As said "config view" can give non operation staff to check if some configs are there or not ... "config editor" is very powerful when you want to edit a never ending access-list, but remember to avoid to use it for complex BGP config... You have been warned !
Conclusion
In this 1st article:
- We presented freeRouter config mode
- Most of these are useful in various different context
Final words
All these modes are not new. IOS, IOS-XR, IOX-XE, NW-OX, JUNOS have their own config mode that are somewhat similar. In any case freeRouter config mode implementation is meant to address all needs from the network operators perspective. As you can observe, configure mode has an impressive list of mode. Feel free to try and use them according to your environment taste!
Last but not least, you can play with these different mode from this sandbox:
telnet dl.nop.hu 1 ↵ Trying 193.224.23.5... Connected to dl.nop.hu. Escape character is '^]'. XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXX XXXXX XXX XXX XXX XX XX XXXX XXXXXXXXXXXXXXXXXXX XXXX XXXX XX XXXX XX XXXX XX XX XX XXXX XXXXX/~~~~~~\XXXXXX XXXX X XXX XX XXXX XX XXXX XX XX XX XXXX XXXX| player |XXXXX XXXX XX XX XX XXXX XX XXX XX XXXX XXXXX\______/XXXXXX XXXX XXX X XX XXXX XX XXXXXXX XX XX XXXX XXXXXXXXXXXXXXXXXXX XXXX XXXX XX XXXX XX XXXXXXX XX XX XXXX XXXXXXXXXXXXXXXXXXX XXXX XXXXX XXX XXX XXX XXX XX XXX XXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX welcome line ready menu lab: ...
ssh dl.nop.hu -l random_user 1 ↵ Warning: Permanently added 'dl.nop.hu,193.224.23.5' (RSA) to the list of known hosts. random_user@dl.nop.hu's password: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXX XXXXX XXX XXX XXX XX XX XXXX XXXXXXXXXXXXXXXXXXX XXXX XXXX XX XXXX XX XXXX XX XX XX XXXX XXXXX/~~~~~~\XXXXXX XXXX X XXX XX XXXX XX XXXX XX XX XX XXXX XXXX| player |XXXXX XXXX XX XX XX XXXX XX XXX XX XXXX XXXXX\______/XXXXXX XXXX XXX X XX XXXX XX XXXXXXX XX XX XXXX XXXXXXXXXXXXXXXXXXX XXXX XXXX XX XXXX XX XXXXXXX XX XX XXXX XXXXXXXXXXXXXXXXXXX XXXX XXXXX XXX XXX XXX XXX XX XXX XXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX welcome line ready menu lab: # - reboot router1 $ - reboot router2 % - reboot router3 1 - connect to router1 2 - connect to router2 3 - connect to router3 ^ - rebuild routers l - connect to lg.nop.dn42 x - exit choose:1 - attach vdc lab1 yourname# yourname#configure ? <cr> banner - edit the banner editor - configure from editor file - append to running configuration network - append to running configuration overwrite-network - overwrite the running configuration reapply - !!!EXPERiMENTAL!!! try to reapply current configuration reload - overwrite the startup configuration replace - overwrite the running configuration revert - revert to startup configuration rollback - configure within auto-revert session startup - edit the startup configuration terminal - configure from this terminal viewer - view current configuration yourname#configure ...
In order to exit the sandbox session use the following escape sequence: Ctrl-c + Ctrl-x
Another method to access the sandbox, by click here, this will open a terminal webapp into your browser:
