Inbound DID call getting error when following Alias attempting to reach FXS port in SRST mode

[Justin Estermann]

Last evening I was working on configuring SRST failover for a site with a 2911 ISR and PRI. IOS version is 15.1(4)M3. CUCM version is 8.6.2.22900-9.

Most of the fallback configuration was already in place previously, however since replacing analog trunks with a PRI, I hadn't yet configured the DID's to work in SRST mode.

The ISR is setup to use H.323 for the PRI to reach CUCM during normal operations, and the FXS ports are configured with MGCP from CUCM during normal operations. Normal operations work fine.

In failover (SRST mode), inbound DID calls follow the alias commands as intended, as long as they're going to ephones.

I found I had to add a destination-pattern under the "dial-peer voice xxxxxx pots" dial peers that were associated with the FXS voice ports, to allow ephones to call the FXS ports while in SRST mode. The way I read documentation, I originally thought the FXS ports got the necessary configuration from CUCM, to allow them to fully work in SRST mode, however that did not seem to be the case. In CUCM, all of the FXS ports are in device pools that specify the same SRST config that the ephones have in their device pool.

Additionally, the FXS ports are able to dial the DNs on the ephones, as intended.

Here's the problem I ran into: While in SRST mode, when a DID call comes in on the PRI, and follows the alias for the DID to the destination pattern on the voice port's dial peer, the router throws an error, and the inbound call fails.

A snippet of the error is "VOICE_IEC-3-GW: H323: Internal Error (Socket error)".

Here is what the fallback config looks like:

call-manager-fallback
 secondary-dialtone 9
 max-conferences 8 gain -6
 transfer-system full-consult
 ip source-address 10.10.10.1 port 2000
 max-ephones 58
 max-dn 300 octo-line preference 2
 system message primary Network Down Contact IT Svcs
 huntstop channel 6
 pickup 53440
 alias 1 72240 to 26701 preference 1 <--this is a DID to an ephone
 alias 2 77040 to 26701 preference 1 <--this is a DID to an ephone
 alias 3 57227 to 72242 preference 1 <--this is a DID to FXS port 0/2/2

Here are the dial peers for the FXS voice ports:

dial-peer voice 999021 pots
 service mgcpapp
 destination-pattern 26709
 port 0/2/1
!
dial-peer voice 999022 pots
 service mgcpapp
 destination-pattern 72242
 port 0/2/2
!
dial-peer voice 999020 pots
 service mgcpapp
 destination-pattern 26708
 port 0/2/0

Here are the FXS voice ports:

voice-port 0/2/0
 timeouts interdigit 4
 connection plar 918777464674
 description Phys Therapy-H Lang Svc
 station-id name Phys Therapy-H Lang Svc
 station-id number 26708
!
voice-port 0/2/1
 timeouts interdigit 4
 description Phys Therapy-H Courtesy
 station-id name Phys Therapy-H Courtesy
 station-id number 26709
!
voice-port 0/2/2
 timeouts interdigit 4
 description Phys Therapy-H Fax
 station-id name Phys Therapy-H Fax
 station-id number 77242

I also have the following lines in the config, as needed for MGCP fallback:

ccm-manager fallback-mgcp

application
 global
  service alternate Default

Any help with this is appreciated.

Thanks!

[Dennis Mink]

Justin

you have H323 configured as fall back, you have individual dial peers that is all good.

Have you got an H323 bind source IP address configured at all?

cheers

[Justin Estermann]

Yes. Under the interface loopback...

interface Loopback0
ip address 10.10.10.1 255.255.255.255
h323-gateway voip interface
h323-gateway voip bind srcaddr 10.10.10.1

[Justin Estermann]

It appears that the error generated when the call comes in is more important that I think I realized.

The full error is: VOICE_IEC-3-GW: H323: Internal Error (Socket error): IEC=1.1.186.5.7.5

The IEC=1.1.186.5.7.5 is the important part, I think.

"show voice iec description 1.1.186.5.7.5" reveals the following:

    IEC Version: 1
    Entity: 1 (Gateway)
    Category: 186 (Signaling socket failure)
    Subsystem: 5 (H323)
    Error: 7 (Socket error)
    Diagnostic Code: 5

Can anyone help me make sense of this, in the context of the scenario I described in my original post?

Thanks!

[Marcelo Morais]

Hi,

beyond the:

show voice iec description

try the following commands:

debug ip tcp transaction
debug cch323 h225
debug isdn q931

and make a call again ... please, post the result.

Hope this helps