You learn it on your first day: we delete commands by prefixing them with the word ”no”, e.g.
ip address x.x.x.x
no ip address
no int loop0
Sometimes it is not that easy, though. Let’s enter the following commands:
default information-originate route-map MYMAP
no default information-originate route-map MYMAP
What are we left with? Let’s see:
show run | s router
OMG!!! We have potentially caused an outage, because we have only deleted a condition on which sending a default-route was based and now the default route is still sent out, unconditionally. This is something like forgetting the word ”add” in switchport trunk vlan 10 (instead of: add 10)
Not a very nice thing in a production environment.