Dial Plan Question - Directory Numbers

[voip7372]

Regarding CUCM 10.5:

CUCM is still a little new to me in some areas and I'm still trying to wrap my head around the dial plan options.  I have an Avaya background and I understand dial plans and call routing very well in Avaya, but in CUCM 10.5, I see there is more flexibility with dial plans but it also can get very confusing and complex.  

My question is this.  I've seen a working system (a single CUCM cluster that serves multiple countries) where all the DNs were setup to match the real outside phone number, except there's an 8 in front.  For example, the real outside number might be (just making up something for the example) 4912355544411.   So in this case, internally the DN is 84912355544411.  

Assuming that we don't want to use E.164 numbers as our DN in CUCM and knowing all the features available in CUCM 10.5, can someone explain to me the logic or advantage behind using a leading 8 plus the real outside number (including country code) as the directory number?  Again, I've seen a system setup this way and so far I'm not sure what the purpose of the leading 8 is, because I was thinking that any full outside number (with country code) would always be unique worldwide, so if that's the case, what's the harm in using the real outside number but WITHOUT the extra 8 in front as the DN?  I guess there must be some reason why it was configured this way and perhaps it was related to trying to avoid inter-digit timers and number conflicts of some sort, but so far the reasoning for this eludes me.   

Thanks!

[Lisandro Quinteros]

Well I have never seen that.. maybe its an extrange way of globallization where they use 8 insted of + and they have their global patterns as 8! ???

And they use that extrange global number for teho cfwd unregister or other features..

Any other ideas ?

[voip7372]

The 8 in front of the other digits for each person's DN is of course only for internal use, but so far I haven't figured out why the dial plan was arranged this way.  I've also seen a Cisco presentation about dial plans and there were some examples of DNs with an 8 in front of the real outside number (used as the DN), but there was never any detailed explanation as to why they were using 8 plus the outside number as a DN rather than only the real outside number as the DN.   I'm sure there must be some reasoning behind it. 

[Brandon Pierce]

8 is generally used to get an outside dialtone from CUCM.  When the user picks up and presses 8, they hear a second dialtone and then dial the number.  It is easier to setup route patterns when you normalize the dial plan for 7,10,11 digits and international in this way as well. 

This guy explains it well too: http://www.tatertotsforthemasses.com/2010/09/why-do-we-dial-9.html

For my organization, we use 8 and every install we do, we also use 8.  9. is to easy to accidentally dial 911 due to user error.

[Francisco Granados]

Great tip! 

[Lisandro Quinteros]

Well could be but for me is has no sense you could have using 4 5 8 .... extension lenght and then just add a translation pattern for  each pstn numbers of each branch.. so if you try to call to Germany with E164 the translation will strip the + the country code and translate to DN number...

For me the only reason that could be is due to incompatibility of + as someone says .. Maybe the take their dial plan from and old version of cucm where + not supported.. does anyone knows if in version 4 was supported ?

By the way 7960 supports + at least with the firmware I have here..

Lisandro

[voip7372]

We're not using + for anything at the moment.  The DNs all begin with 8.  

[voip7372]

Not in this case.  We don't use 8 for outside access anywhere.  We use 9 in the US and UK, 0 in much of the rest of Europe.  My question is more about the DN, but the dial plan in general too (as it relates to using DNs that begin with 8).  Again, in my example, the DN of a person is truly 8 plus their real outside number.  8 is part of their DN.  8 has nothing to do with outside dialing in this example.    

[Brandon Pierce]

My guess for an 8 on their full E.164 DN on the phone would be to categorize calling permissions in much the same way you would do for outbound calls.  I've never personally seen it setup that way.

[voip7372]

Thanks, Brandon.  It seems like this is becoming a real mystery then (the reasoning behind this arrangement).   I have some Cisco contacts locally and if I can't get a good explanation here on the forum, I guess I can ask Cisco too and see if they're aware of a reason why someone would make the DNs this way.  I'm sure there has to be some explanation for it, but I'm just hoping the explanation isn't something like "when we originally purchased Call Manager at release 4 or whatever it was, someone suggested that we create the DNs with this numbering scheme".   I'm one of those types of people that isn't content to know something works and just keep going with it the same as before.  I like to know the reasoning for it because it's easier to troubleshoot and also know if there's a better, more appropriate way to do it because of new functionality that wasn't available in the past.     

[Brandon Pierce]

Yeah, normal installs for me over the years has always been 4 or 5 digit extensions then just mask it as a E.164 number on the line or RP.  Not sure why they would be doing the full E.164 then an 8 locally....  Normally gateways and trunks manage incoming calls, you could check there to see if they got anything funky going on with CSS's inbound.

[voip7372]

I was just looking at the gateways in CUCM (Cisco routers/h.323 gateway), translation patterns and more.  It looks like I may have to go back to the person that originally configured all this and find out why he did it.  I don't see anything unusual there (all digits coming in are accepted and there's no digit manipulation of any kind.

The thing that caught my attention though was the translation patterns I see.  I see lots of TPs assigned that match the DN ranges for the various sites (other countries in Europe) and the CSS associated with the TPs would seem to indicate that these digits are expected to be coming from one of the gateways.  So, maybe it was done this way so if a person in France wanted to call our office in Germany on the same cluster but they dialed the number as if it was an external international call, we can catch that at the gateway (router), strip off any leading digits that make it an external call, insert the 8 and send it right back to CUCM where it's seen in the translation patterns and then routed to the user as an internal call.   So, perhaps this is all setup like this for nothing more than being able to easily identify a call that is truly for an internal extension (because all DNs start with 8)?   Know what I mean?    Make sense?   That's the only thing that I came up with when I noticed those translation patterns, without having talked to the original person that configured this....

[Francisco Granados]

Jmeier,

Aside from client preference, the only other thing I have seen is phone limitations. Older phones like 7940/7960s do not fully support globalized dial plans (They can't dial +). 

Thanks,

FG