Cisco ios is strange: deleting commands (and causing an outage)


You learn it on your first day: we delete commands by prefixing them with the word ”no”, e.g.


no shutdown

ip address x.x.x.x

no ip address

int loop0

no int loop0

Sometimes it is not that easy, though. Let’s enter the following commands:

router rip

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

router rip

default information-originate

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.



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