Showing results for 
Search instead for 
Did you mean: 

DID dilemma!

Level 1
Level 1

Hi all,

         I have a confusion regarding DID (direct inwards dialing).


         when an organization purchases a range of numbers for DID/DOD, does the organization have to use that range for internal and external purposes or else can we assign just any range to our network and use purchased DID range for DID/DOD

Ex: xx xxx 654 31442 ; where xx is country code, xx - state code, xxx 61000 to xxx 61999 - DID/DOD range.

now can i assign 7xxxx to any phone and use the above range to send that call in and out to PSTN.

Can you suggest me a book for understanding Dial plans in enterprise environments for analog/digital/Voip implementations.


5 Replies 5

tobin hawkshaw
Level 1
Level 1

Think of it as private/public IP addresses

You can do what you want inside your network but if you would like those numbers to be reachable from the PSTN you need to map the public PSTN numbers onto internal numbers.

You can do this a number of ways CUCM = incoming call settings, translation patterns or just one to one mappings using inbound significant digits (just like NAT'ing)

CUCME = voice translation rules, dialplan patterns (dont use these) etc...

You will also have to translate the internal CLI/ANI to a recognisable PSTN number within your range for outbound calls as most Line suppliers dont like you setting the CLI/ANI outside of your range, not to mention its frowned upon legaly.

I found this snippet which may help,

Its probably not worth a whole book as you only need to grasp a couple of concepts.


Is it legal, to use a number apart from range provided and apply translation pattern on it , while sending it out to PSTN as a number from the range provided.The provider will not have a clue of what has been translated rite or do they.

You can change it to whatever you want internally, the line supplier doesn't know or care, its actually pretty normal.

if you are talking about a system that takes an inbound call from one number and hairpins the call using its own number like a two stage dialing setup then yes, you can do that, its what most calling card ISR systems do anyway.

Just the same as IP address ranges, internal and external; internaly you can do what you want but in order for any external traffic to work its needs translating to a public address you have been provided.

Dont worry about the external CLI to much, just translate you PSTN numbers to whatever you want to internaly and give the outbound calls a go, if its not working out, check what your sending to the line supplier and confirm with them what they want to see. Some wont care as they will overwrite it, others are picky.

sorry, the legality issue is usually only to stop you from setting your CLI/ANI/Calling number to be premuim rate, its to stop missed call type scams.

Thanks Tobin

I read designing a dial plan is probably the biggest headache while implementing a voip network.

can i find book which details about interanl processing that takes place in CUCM, which resources are used for which process, the internal architecture of CUCM etc.

you could go with the implementation books based around CIPT

Implementing Cisco Unified Communications Manager part1 (this is probably the most appropriate)

Implementing Cisco Unified Communications Manager part2