[cisco-voip] FACILITY / Mandatory information element missing on ISDN PRI to PBX

[Zoltan.Kelemen at emerson.com]

Hi,

A IOS Gateway is given that connects through a E1 ISDN PRI to a Nortel PBX, The router acting as network side. (primary-net5)

Calls are coming in through a SIP trunk from two different CUCM clusters (both being trunked to a central CUCM cluster that only acts as a call router).

Call setup works in both cases, SIP messages seem identical (through debug ccsip messages)
However, once the call is established, on calls coming from "SITE A", a FACILITY message is sent towards the PBX, with no information element. Because of this the PBX throws an error and the gateway disconnects:

Jan 28 12:55:44.291 UTC: //478350/9DBBB8800000/CCAPI/cc_api_call_facility:
   Interface=0x311D76B8, Call Id=478350
Jan 28 12:55:44.291 UTC: //478351/9DBBB8800000/CCAPI/ccCallFacility:
   Call Id=478351
Jan 28 12:55:44.291 UTC: ISDN Se0/0/0:15 Q931: TX -> FACILITY pd = 8  callref = 0x0423
Jan 28 12:55:44.311 UTC: ISDN Se0/0/0:15 Q931: RX <- STATUS pd = 8  callref = 0x8423
        Cause i = 0x81E0 - Mandatory information element missing
        Call State i = 0x0A
Jan 28 12:55:44.311 UTC: ISDN Se0/0/0:15 Q931: TX -> DISCONNECT pd = 8  callref = 0x0423
        Cause i = 0x82E0 - Mandatory information element missing
Jan 28 12:55:44.355 UTC: ISDN Se0/0/0:15 Q931: RX <- RELEASE pd = 8  callref = 0x8423
Jan 28 12:55:44.355 UTC: ISDN Se0/0/0:15 Q931: TX -> RELEASE_COMP pd = 8  callref = 0x0423

Calls from "SITE B" never generate this facility message so the call works as expected.

I tried to block forwarding of facility messages altogether on the PRI, but it doesn't seem to make any difference (not even after restarting the serial interface):

interface Serial0/0/0:15
description VOICE|E1 PRI towards local Nortel PBX
no ip address
encapsulation hdlc
isdn switch-type primary-net5
isdn protocol-emulate network
isdn incoming-voice voice
no isdn outgoing ie facility
no cdp enable
!

Any clues as to what triggers the facility manager in the CUCM setup and/or how can I block this on the gateway?

Thanks,
Zoltan Kelemen
Emerson

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