CoR on CME

December 7, 2011

While I have written about CoR in a distant past, when I look back at it I don’t think I did a great job of explaining the underlying concept. I really focused on configuration without regards to whether or not someone understood why we were configuring certain things, or for that matter why we configuring CoR at all. Now I’m going to try and rectify that situation.

If you are unfamiliar with Class of Restrictions on CallManager Expresss, you might have someone try to describe it in the context of calling search spaces on Communications Manager, but what if you don’t really have a grasp of what those are? Rather than explaining a technical concept with another technical concept, I’d just like you to meet my friend Bubba, Bubba CoR.

You should probably just call him Mr. CoR though. Mr. CoR is the doorman/bouncer of your CME, but unlike most bouncers he won’t let you in because you are attractive or slip him a twenty. He has a strict list and if the list doesn’t allow you to go then you don’t go. His list is pretty unique too. Instead of dealing with a simple fact of whether your name is on the list it deals with who you know that the person you are talking to knows. At the risk of getting into a never ending spiral, let’s have an example within an example and take a trip back to the 80s.

For this example, we wll pretend that you are a scrappy youth named Arnold and that you want to talk to your brother, Willis. The fact that you know Willis isn’t enough, you need to know someone that Willis also knows. Let’s take a look at who these two kids know:



So, because Arnold and Willis both know Mr. Drummond, Mr. CoR will allow them to speak to one another. However, because The Gooch doesn’t know Mr. Drummond, he will not be able to call Willis. That would be an extreme nutshell version of CoR on CME. Now that we have this explanation, we can cover the actual technical nuts and bolts and see if the explanation above helps out. 
So that the mapping works out appropriately, I’m going to do some name mapping from our example above so that you can sort of reference it back to the example above:

    • Arnold will change to: Arnold-Outbound
    • The Gooch will change to: Gooch-Outbound
    • Willis will change to: Call-International
    • Dudley Ramsey will change to: LD
    • Mr. Drummond will change to: International
    • Miss Chung will change to Local
    • Robbie Jason will change to TollFree

Now, the naming convention doesn’t matter that much as long as you are comfortable with how it fits into your organization. The first thing that we need to do is configure the system with the classes of restrictions. This equates to the names of the people that each kid knew up above. Here is an example of how this would look:

dial-peer cor custom
  name Local
  name LD
  name Internationa
  name TollFree

At this point, nothing is really happening. We are just defining names that we will use in the next step of the process. Now we will configure the “lists of who they know”:

dial-peer cor list Arnold-Outbound
  member Local
  member LD
  member International
  member TollFree

dial-peer cor list Gooch-Outbound
  member Local
  member TollFree

dial-peer cor list Call-International
  member International

dial-peer cor list Call-Local
  member Local

dial-peer cor list Call-TollFree
  member TollFree

As you can see, we have defined each of the “kids” and put in a member statement for who they “know”. This still isn’t doing anything for us yet though because it hasn’t been applied. Let’s get to that now:

ephone-dn 1
  number 1001
  name Arnold
  cor incoming Arnold-Outbound

ephone-dn 2
  number 1002
  name The Gooch
  cor incoming Gooch-Outbound

So that’s the first half of applying the configuration. You will notice that when you implement CoR on the ephone-dn for restricting who the user can call, you will use the key word “incoming” this is the direction of the call with relation to the CME router. When you dial a number it has to come INTO the router first to be processed. Note that if you wanted to restrict who could call a phone, you could have an outgoing CoR applied to the ephone-dn in addition to the outgoing CoR.
The second half of applying the configuration is below:

dial-peer voice 1 pots
  description local calling - Miss Chung
  destination-pattern 91800[2-9]......
  cor outgoing Call-TollFree

dial-peer voice 9011 pots
  description International Calling - Mr. Drummond
  destination-pattern 9011T
  cor outgoing Call-International

The above has been shortened just to make it brief. As you can see, we have applied am outgoing CoR to these dial-peers, again because of the direction in relation to the router. You can also have incoming CoR on dial-peers if they are going to be hit as an incoming dial-peer. Now that this configuration is in place on your router, your class of restrictions will be active and The Gooch will only be able to dial local and toll free while Arnold will be able to dial pretty much anywhere. Maybe if The Gooch wasn’t such a bully he would be able to call more places.
Hopefully this humorous short trip back to the 80s will help you in your understanding of CoR on CME. If it didn’t, you might want to keep it to yourself or you might get a visit from Bubba CoR. What’chu Talking’ ’bout Willis?


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