Loop Detected on SIP Trunk between CUCM & VCS

Unanswered Question
Aug 9th, 2012

Hi all,

As recent trend of CUCM & VCS integration, our office has followed the same to build a SIP trunk betweem CUCM & SIP. I have checked IPphone from CUCM side can call to video endpoint successfully, but there is loop detected on the call from video endpoint registered to VCSc to IPphone.

Is there anyone can tell what Loop detected means? What I should check to investigate the issue? Please help kindly advise.

Below is the call search log:

VCS to CUCM
CUCM to VCS

Search (15)

        State: Completed

        Found: False

        Reason: Loop detected

        Type: H323 (LRQ)

        CallSerial Number: 3ee834d0-e231-11e1-9a3e-0010f316eb04

        Tag: 3ee83606-e231-11e1-8dc9-0010f316eb04

        StartTime: 2012-08-09 22:48:13

        Duration: 1.24

        Source (1)

            Authenticated: False

            Aliases (1)

                Alias (1)

                    Type: H323Id

                    Origin: Unknown

                    Value: 29315101

            Zone (1)

                Name: DefaultZone

                Type: Default

        Destination (1)

            Alias (1)

                Type: H323Id

                Origin: Unknown

                Value: 29531403

        SubSearch (1)

            Type: Transforms

            Action: Not Transformed

            ResultAlias (1)

                Type: H323Id

                Origin: Unknown

                Value: 29531403

            SubSearch (1)

                Type: Admin Policy

                Action: Proxy

                ResultAlias (1)

                    Type: H323Id

                    Origin: Unknown

                    Value: 29531403

                SubSearch (1)

                    Type: FindMe

                    Action: Proxy

                    ResultAlias (1)

                        Type: H323Id

                        Origin: Unknown

                        Value: 29531403

                    SubSearch (1)

                        Type: Search Rules

                        SearchRule (2)

                            Name: LocalZone Match1

                            Zone (1)

                                Name: LocalZone

                                Type: Local

                                Protocol: H323

                                Found: False

                                Reason: Not Found

                                Gatekeeper (1)

                                    Address: 172.30.88.21:0

                                    Alias (1)

                                        Type: H323Id

                                        Origin: Unknown

                                        Value: 29531403

                            Zone (2)

                                Name: LocalZone

                                Type: Local

                                Protocol: SIP

                                Found: False

                                Reason: Not Found

                                Gatekeeper (1)

                                    Address: 172.30.88.21:0

                                    Alias (1)

                                        Type: H323Id

                                        Origin: Unknown

                                        Value: 29531403

                        SearchRule (3)

                            Name: Zone001 Match1

                            Zone (1)

                                Name: VF Corporation VCS

                                Type: Neighbor

                                Protocol: H323

                                Found: False

                                Reason: Loop detected

                                Gatekeeper (1)

                                    Address: 10.1.48.21:1719

                                    Alias (1)

                                        Type: H323Id

                                        Origin: Unknown

                                        Value: 29531403

                            Zone (2)

                                Name: VF Corporation VCS

                                Type: Neighbor

                                Protocol: SIP

                                Found: False

                                Reason: Internal Server Error

                                Gatekeeper (1)

                                    Address: 10.1.48.21:5060

                                    Alias (1)

                                        Type: H323Id

                                        Origin: Unknown

                                        Value: 29531403

                        SearchRule (4)

                            Name: Zone003 Match1

                            Zone (1)

                                Name: VEBBVCS1

                                Type: Neighbor

                                Protocol: H323

                                Found: False

                                Reason: Loop detected

                                Gatekeeper (1)

                                    Address: 172.20.104.21:1719

                                    Alias (1)

                                        Type: H323Id

                                        Origin: Unknown

                                        Value: 29531403

                            Zone (2)

                                Name: VEBBVCS1

                                Type: Neighbor

                                Protocol: SIP

                                Found: False

                                Reason: Internal Server Error

                                Gatekeeper (1)

                                    Address: 172.20.104.21:5060

                                    Alias (1)

                                        Type: H323Id

                                        Origin: Unknown

                                        Value: 29531403

                        SearchRule (5)

                            Name: Zone004 Match1

                            Zone (1)

                                Name: VEBB7EXW7

                                Type: TraversalClient

                                Protocol: H323

                                Found: False

                                Reason: Destination not found

                                Gatekeeper (1)

                                    Address: 212.123.3.175:6001

                                    Alias (1)

                                        Type: H323Id

                                        Origin: Unknown

                                        Value: 29531403

    Search (16)

        State: Completed

        Found: True

        Type: H323 (LRQ)

        CallRouted: True

        CallSerial Number: e650782e-e234-11e1-9eb5-0010f316eb04

        Tag: e6507964-e234-11e1-a696-0010f316eb04

        StartTime: 2012-08-09 23:14:22

        Duration: 0.01

        Source (1)

            Authenticated: False

            Aliases (1)

                Alias (1)

                    Type: H323Id

                    Origin: Unknown

                    Value: 29531403

            Zone (1)

                Name: CUCM Neighbor

                Type: Neighbor

        Destination (1)

            Alias (1)

                Type: H323Id

                Origin: Unknown

                Value: 29315101

        SubSearch (1)

            Type: Transforms

            Action: Not Transformed

            ResultAlias (1)

                Type: H323Id

                Origin: Unknown

                Value: 29315101

            SubSearch (1)

                Type: Admin Policy

                Action: Proxy

                ResultAlias (1)

                    Type: H323Id

                    Origin: Unknown

                    Value: 29315101

                SubSearch (1)

                    Type: FindMe

                    Action: Proxy

                    ResultAlias (1)

                        Type: H323Id

                        Origin: Unknown

                        Value: 29315101

                    SubSearch (1)

                        Type: Search Rules

                        SearchRule (2)

                            Name: LocalZone Match1

                            Zone (1)

                                Name: LocalZone

                                Type: Local

                                Protocol: H323

                                Found: True

                                Gatekeeper (1)

                                    Address: 172.30.88.21:0

                                    Alias (1)

                                        Type: H323Id

                                        Origin: Unknown

                                        Value: 29315101





I have this problem too.
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aljaiswa Thu, 08/09/2012 - 08:44

Hi Bell,

The VCS has capability to detect the call as getting looped to stop to use all the resources for a single call.

for e.g. consider a scenario you make a call and you have a nieghbour zone betweev two VCS.

Endpt-->VCS-A<-->VCS-B<--Endpt

now you made a call. the request goes to VCS-A. it checks search rules and sends calls to VCS-B and because of wrong call routing the VCS-B sends the call back to VCS-A.

now VCS-A has a loop detection option!! if its ON it will come to know its the same call coming back to it which VCS-A has sent to VCS-B. at this point VCS-A can go on to match other search rules or it can drop the call based on subsequent search rules created on VCS.

This is related to search rules configured on the VCS and the priority and the Regex basically you are matching.

in your deployment you can fix the issue after modifying the searh rules and matching proper Regex!!

Thanks

Alok

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