Wednesday, 22 February 2012

A policy-map, by any other name

Time is a valuable resource in the lab.   In a lab task, if asked to configure a policy-map named “BOB”, it doesn’t get the same point value if we happen to accidentally name it “bob”, especially  if they are looking to see if you configured what they asked for. The challenge is, that when reviewing a lab task, and we discover that we need to change a name, it could be a hassle, as we need to remove the policy-map, recreate the policy map, and then put it in place again.
So if you are down to the last minute, here is a time saving solution, that can assist with that process.
IOS allows us to rename a policy-map, and the IOS will swap out the name in other areas of the configuration that reference that policy map.
Here is an example, of a policy map from Volume 2, lab 5.

Rack1R5#show run policy-map
Building configuration...

Current configuration : 352 bytes
!
policy-map TRANSIT_RATE_LIMIT
class FRAGMENTS
   police rate 1000000 pps burst 200000 packets
policy-map type port-filter HOST_PORT_FILTER
class CLOSED_PORTS
   drop
policy-map CEF_EXCEPTION_RATE_LIMIT
class class-default
   police rate 100 pps burst 20 packets
policy-map HOST_RATE_LIMIT
class ICMP
   police rate 10 pps burst 5 packets
!
end

Rack1R5#show run | begin control
control-plane host
service-policy input HOST_RATE_LIMIT
service-policy type port-filter input HOST_PORT_FILTER
!
control-plane transit
service-policy input TRANSIT_RATE_LIMIT
!
control-plane cef-exception
service-policy input CEF_EXCEPTION_RATE_LIMIT
Let’s say that after reviewing our configuration, we discovered that the policy-map for the cef-exception sub interface of the control plane should have been named “NEW-NAME-CEF”.
To change it everywhere in the configuration, instead of creating it new, and replacing it, we could simply do this:
Rack1R5(config)#policy-map CEF_EXCEPTION_RATE_LIMIT
Rack1R5(config-pmap)#rename NEW-NAME-CEF
Now, when we look at the configuration, we can see that not only the name has changed for the policy-map, but it also updated our control-plane configuration to reflect the new name there as well:
Rack1R5#show run policy-map
Building configuration...

Current configuration : 340 bytes
!
policy-map TRANSIT_RATE_LIMIT
class FRAGMENTS
   police rate 1000000 pps burst 200000 packets
policy-map type port-filter HOST_PORT_FILTER
class CLOSED_PORTS
   drop
policy-map NEW-NAME-CEF
class class-default
   police rate 100 pps burst 20 packets
policy-map HOST_RATE_LIMIT
class ICMP
   police rate 10 pps burst 5 packets
!
end

Rack1R5#show run | begin control
control-plane host
service-policy input HOST_RATE_LIMIT
service-policy type port-filter input HOST_PORT_FILTER
!
control-plane transit
service-policy input TRANSIT_RATE_LIMIT
!
control-plane cef-exception
service-policy input NEW-NAME-CEF
!

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Chitika