show run all to the rescue

This is gonna be a quick post!

Ever drawn a blank when trying to recall a specific command? You know what you're looking for and it's on the tip of your tongue. Well, I like to use the command show run all to look for the answer. If used right it can quickly find you the default of a command that would otherwise be omitted from regular show run command.

Of course, when looking for something specific, the command show run all won't help much, unless your objective is to wear down the spacebar on the keyboard. To find something specific it will have to be piped to either include some keywords or with the section command to filter out all the insane amounts of default commands.

Below is an example of the command used to show all the configured commands on interface FastEthernet2 on a Cisco 881 router. It lists all the commands configured on the interface that wouldn't be seen under normal circumstances.

AMBO-RT#sh run all | section interface FastEthernet2
interface FastEthernet2
 switchport access vlan 10
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 1
 switchport trunk allowed vlan 1-4094
 switchport mode access
 switchport voice vlan none
 switchport priority extend none
 switchport priority default 0
 mtu 1500
 no ip address
<further output omitted - it goes on for a while>

So, this command could be just the thing needed to jog your memory, when drawing a blank.

Also, if you like to read CLI output, like Joe Pantoliano reads the Matrix, go ahead and do a show run all and take it from the top - you will be amazed how many commands you never knew existed.

Configure Replace

If you plan on loading a lot of different topologies into your lab - be it physical or logical - you may want to consider learning the configure replace command to speed things up a bit. What this command can do for you in the lab is to cut down on the time it takes to "reset to zero" by having a base configuration for your router/switch, that you can then use to overwrite any changes done when tampering with different technologies or lab assignments. What I used to do was to make sure not to write anything to the config and then when I needed to reset the lab I would reload the devices and wait the excruciatingly long time it took for them to reload (this was with my hardware lab consisting of a couple of 2600 routers). When I started building a lab setup for my CCIE I knew I had to find a way to change configs faster and I found that this command would help me do just that.

This is how I setup my lab routers  (the routers I use are CSR1000v - Ciscos virtual cloud routers).

You boot up your router and configure the things you want to be configured just about always.

enable
configure terminal
!
hostname R1
!
logging buffered 8192
!
no aaa new-model
!
no ip domain lookup
!
no ip http server
no ip http secure-server
!
line con 0
 exec-timeout 0
 logging synchronous
!
end

When you are done setting up the very basics  - save the running-config to a file on flash.

copy running-config flash:/config/base.conf

Now, whenever you have configured anything on the router - like, say, some DMVPN or EIGRP configuration - and you want to reload it to the base to start another lab, this is what you do.

From the privileged exec mode enter the following command

R1#configure replace flash:/config/base.conf force
Total number of passes: 1
Rollback Done
R1#
*Nov 12 10:30:42.186: Rollback:Acquired Configuration lock.
R1#

This makes the running-config identical that of the base.conf file saved earlier. The "Total number of passes: 1" indicates it took 1 pass of the config to make it identical. The amounts of passes it will take depends on how much the runnin-config and the base.conf file differs.

There is a bit more to the command if you want to use it outside of the lab, but this just about covers what you may want in a lab environment.