CFA - Loop prevention - CUCM7

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Mar 14th, 2009
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Hi Forum,


I have a question regarding the new Call Forward All - loop prevention feature in CUCM 7.0.


As tested in my lab I'm not able to make a cfa in the following scenario:


phone 1, DN 1000/pt-phones

phone 2, DN 1000/pt-manager


If I now try to forward the phone 1 (DN1000/pt-phones) to phone 2 I get a reorder.


Is this behavior "works as designed"? I don't thinks so, because in the dial-plan it's another DN and should of course be possible.


Is there maybe a service parameter to disable the loop prevention feature to test if this is the problem.


Best regards



Torsten

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Rob Huffman Sat, 03/14/2009 - 15:33
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Hi Torsten,


This sounds more like a CallFWD CSS (Calling Search Space) issue to me :) Does the CFWD CSS on the phone 1, DN 1000/pt-phones have access to /pt-manager ?


Hope this helps!

Rob


Jaime Valencia Sat, 03/14/2009 - 17:46
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just to add to the info from Rob there has always been a kind of loop prevention system embedded, CUCM will only allow 12 hops before returning reorder.

my guess is you have the partition from your own phone with higher preference than the one from the manager in the CSS. if that's the case it'w WAD, on your scenario CUCM won't even go thru the 12 hops as it already knows it's looped.


HTH


java


if this helps, please rate

gogasca Sun, 03/15/2009 - 01:03
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java in 7.X u get an automatic message for Loop prevention as soon as u try to do the CFall.

Why dont u try first of all the basic test.

Phone 1001 none partition

Phone 1002 none partition


Try to fwd 1002 to 1001

try to fwd 1001 to 1002 here u will the error.


then check CSS and partitions as Rob suggested.

torsten.brink Sun, 03/15/2009 - 03:27
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Hi All,


thanks for the answers.


I don't think that this is a css problem.


Here's my constellation:


phone 1 cfa css: css-manager

-> pt-manager


If I try to forward 1000/pt-phones to 1000/pt-manager I only get a reorder.


Unfortunaley there is no message for "loop detected" in the display.


Funny thing, it's not possible that the DN with 1000/pt-phones is reached, because the css has not the partition.


Cheers


Torsten.

Rob Huffman Sun, 03/15/2009 - 06:42
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Hi Torsten,


I don't think you are getting the "loop detected" message in the display because this is not detected as a "loop".


What this mechanism is trying to prevent is this;


I decide to go fo Coffee, so I try to Call Forward my phone DN 5555 to Gonz @ 4444. Meanwhile Gonz @ 4444 has left for a meeting so he has Call Forwarded to Java @ 3333. Java is attending the same meeting so he has set Call Forward to me @ 5555.


When I attempt to Call Forward in this scenario (because of the existing CFWD's that Gonz and Java have set) I will receive the "Loop Detected" message on my phone display.


Here are the notes for Call Forward Loop Detection. Please note the line *** below;


Call Forward All Loop Prevention and Breakout


Cisco Unified Communications Manager prevents Call Forward All activation on the phone when a Call Forward All loop is identified. For example, Cisco Unified Communications Manager identifies a call forward loop when the user presses the CFA softkey on the phone with directory number 1000 and enters 1001 as the CFA destination, and 1001 has forwarded all calls to directory number 1002, which has forwarded all calls to directory number 1003, which has forwarded all calls to 1000. In this case, Cisco Unified Communications Manager identifies that a loop occurs and prevents CFA activation on the phone with directory number 1000.


Call Forward All loops do not impact call processing because Cisco Unified Communications Manager supports CFA loop breakout, which ensures that if a CFA loop is identified, the call goes through the entire forwarding chain, breaks out of the Call Forward All loop, and completes as expected, even if CFNA, CFB, or other forwarding options are configured along with CFA for one of the directory numbers in the forwarding chain. For example, the user for the phone with directory number 1000 forwards all calls to directory number 1001, which has forwarded all calls to directory number 1002, which has forwarded all calls to directory number 1000, thus creating a CFA loop. In addition, directory number 1002 has configured CFNA to directory number 1004. The user at the phone with directory number 1003 calls directory number 1000, which forwards to 1001, which forwards to 1002. Cisco Unified Communications Manager identifies a CFA loop, and the call, which breaks out of the loop, tries to connect to directory number 1002. If the No Answer Ring Duration timer expires before the user for the phone with directory number 1002 answers the call, Cisco Unified Communications Manager forwards the call to directory number 1004.


For a single call, Cisco Unified Communications Manager may identify multiple Call Forward All loops and attempts to connect the call after each loop is identified.


Cisco Unified Communications Manager Administration Configuration Tips


If Call Forward All activation occurs in Cisco Unified Communications Manager Administration or the Cisco Unified Communications Manager User Options, Cisco Unified Communications Manager does not prevent the CFA loop.


***If the same directory number exists in different partitions, for example, directory number 1000 exists in partitions 1 and 2, Cisco Unified Communications Manager allows the CFA activation on the phone.




http://www.cisco.com/en/US/docs/voice_ip_comm/cucmbe/rel_notes/7_0_2/cucmbe-rel_notes-702.html#wp581544


Hope this helps!

Rob

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