FXOs from typical service provider

Answered Question
Feb 9th, 2008
User Badges:

I need to know if telephone companys generally offer multiple analog trunks (fxs interfaces) to interface customer fxo's with the same phone number (e.g. 4 analog trunks using the same phone number)so that the customer can just publish one telephone number that would route to a CUE AA and allow multiple incoming calls to the same number. If so is this a common design or solution for such a SMB scenario or is there a better approach?

Correct Answer by gogasca about 9 years 5 months ago

Yes I have seen that with our customers in US.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (4 ratings)
Correct Answer
gogasca Sun, 02/10/2008 - 00:35
User Badges:
  • Green, 3000 points or more

Yes I have seen that with our customers in US.

pcameron Sun, 02/10/2008 - 16:05
User Badges:
  • Cisco Employee,

This is often called a rotary group or line hunting. The telco gives you as many analogue lines as you need , and each one has an individual number to call it directly. They will also configure the first line as the pilot number, so if this first number is busy, the exchange will automatically roll over to the next number in the group.

As you suggested, this allows you to publish one number (sometimes called the LDN or listed directory number), but it will give your callers access to all of the lines.

The telcos should be able offer various hunting schemes such as circular, where the calls cycle through all lines; terminal, where calls always start at the next line and work downwards through the group, and random, where the exchange sends calls on any line in a random fashion.

twissam Sat, 02/16/2008 - 11:30
User Badges:

Interesting answer, good info.

this always happens to us when one of the rotary group line has a problem (from telco), the people would ring to the LDN number and never reaches our VG, it takes a time to figure it out and to talk to telco and ask them to take it out of the hunt.

Any better solution you might suggest!!!

Good day

Rob Huffman Sat, 02/16/2008 - 12:38
User Badges:
  • Super Red, 40000 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 IP Telephony, Unified Communications

Hi Wissam,

Good point! You are correct that these type of problems are often hard to diagnose. Anytime you get a Trouble report of an intermittant "ring no answer" this is the first thing to look at. If you have a telephone "butt-in" you can check the lines involved very quickly and get the Telco to busyout the offending line.

If you want to mitigate the problem you can get the Telco to add a Forward No Answer on the Trunks so that if one goes out of service the calls will still forward past the bad circuit :)

Hope this helps!


paolo bevilacqua Sat, 02/16/2008 - 12:44
User Badges:
  • Super Gold, 25000 points or more
  • Hall of Fame,

    Founding Member

A better solution ? It's called isdn.

Next better is voip - get a reliable itsp and stick with it.


This Discussion