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New Member

No Redundancy for Inbound Calls

We have 2 CallManagers at our organization. Incoming calls are routed to a Unity Auto-Attendant. Whenever the Publisher CallManager is down, calls coming into our organization receive a busy signal. I thought we were setup for redundancy, but I found out the hard way that this was not the case.

We have a 3660 router which routes incoming phone traffic into our organization. On it are two dial peers which route our organization?s incoming calls to the CallManagers. The primary dial peer is supposed to route to the subscriber and the secondary dial peer to the publisher.

1234 is the last 4 digits of our phone number. The dial peer routes to ?Translation Pattern 1234?. Translation Pattern 1234 transforms the digits to 5000. 5000 is a Directory Number on a CTI Route Point. 5000 is set to forward all calls to voicemail. On Unity, we have an Auto-Attendant configured for extension 5000.

Below are the 2 dial peers which route our traffic. I would appreciate anyone taking the time to look at them and offer any suggestions.

CCM 4.0(2a)

Unity 4.05

dial-peer voice 1234 voip

preference 1

incoming called-number .

destination-pattern 1234

progress_ind setup enable 3

voice-class codec 1

voice-class h323 1

session target ipv4:10.10.8.51

dtmf-relay h245-alphanumeric

no vad

!

dial-peer voice 12342 voip

preference 2

incoming called-number .

destination-pattern 1234

progress_ind setup enable 3

voice-class codec 1

voice-class h323 1

session target ipv4:10.10.8.50

dtmf-relay h245-alphanumeric

no vad

1 ACCEPTED SOLUTION

Accepted Solutions
New Member

Re: No Redundancy for Inbound Calls

You do apparantly have a

"voice class h323 1"

configured though, b/c your dial-peer is referencing it with "voice-class h323 1"...

Yes, the command is needed to ensure switchover occurs. See here:

http://cisco.com/en/US/products/sw/voicesw/ps556/products_configuration_example09186a0080094852.shtml

Decrease the H.225 timer on the H.323 gateway to three seconds.

This step is necessary because by default, the H.225 timer that controls redirection to a less preferred dial peer on a "no-response" failure is longer than the ten second timer of the Q.931 Call Proceeding timer. When a call comes in to an H.323 gateway through an ISDN trunk and gets forwarded to an inoperative Cisco CallManager, the router waits for forty seconds before it attempts to use a dial peer with a lower preference, or before it clears the call. By the time this occurs, the ISDN Q.931 that signals on the H.323 gateway has already sent an ISDN Q.931 CALL DISCONNECT to the ISDN switch. The router provides an ISDN clearing code of 0x8066?"recovery on timer expiry."

It is not possible for the H.323 gateway to reset the Call Proceeding timer because it attempts to use a different dial-peer. Therefore, the H.323 gateway must switch peers and complete the call with the help of the secondary Cisco CallManager server within the ten seconds allowed by the Q.931 (Incoming Call Proceeding) timer.

When the H.225 timer is set to three seconds, the router attempts a connection to the primary Cisco CallManager server. If it does not receive a response in three seconds, it falls back to the secondary Cisco CallManager server.

10 REPLIES
New Member

Re: No Redundancy for Inbound Calls

What is your voice-class h323 1 configured as? Does it have "h225 timeout tcp establish 3" or something similar?

Also do you have MGCP configured with fallback configured, or is it a straight h323 gateway?

New Member

Re: No Redundancy for Inbound Calls

Thanks for helping.

I do not have h225 timeout tcp establish 3 setup. It is a straight h323 gateway.

New Member

Re: No Redundancy for Inbound Calls

You do apparantly have a

"voice class h323 1"

configured though, b/c your dial-peer is referencing it with "voice-class h323 1"...

Yes, the command is needed to ensure switchover occurs. See here:

http://cisco.com/en/US/products/sw/voicesw/ps556/products_configuration_example09186a0080094852.shtml

Decrease the H.225 timer on the H.323 gateway to three seconds.

This step is necessary because by default, the H.225 timer that controls redirection to a less preferred dial peer on a "no-response" failure is longer than the ten second timer of the Q.931 Call Proceeding timer. When a call comes in to an H.323 gateway through an ISDN trunk and gets forwarded to an inoperative Cisco CallManager, the router waits for forty seconds before it attempts to use a dial peer with a lower preference, or before it clears the call. By the time this occurs, the ISDN Q.931 that signals on the H.323 gateway has already sent an ISDN Q.931 CALL DISCONNECT to the ISDN switch. The router provides an ISDN clearing code of 0x8066?"recovery on timer expiry."

It is not possible for the H.323 gateway to reset the Call Proceeding timer because it attempts to use a different dial-peer. Therefore, the H.323 gateway must switch peers and complete the call with the help of the secondary Cisco CallManager server within the ten seconds allowed by the Q.931 (Incoming Call Proceeding) timer.

When the H.225 timer is set to three seconds, the router attempts a connection to the primary Cisco CallManager server. If it does not receive a response in three seconds, it falls back to the secondary Cisco CallManager server.

Hall of Fame Super Silver

Re: No Redundancy for Inbound Calls

Couple of things to check:

1. Make sure that the GW in CM references Device Pool that has all the CMs listed.

2. Add the following to your voice H323 class:

voice class h323 1

h225 timeout tcp establish 3

3. Make, sure that the CallManager service is running on all servers.

Chris

New Member

Re: No Redundancy for Inbound Calls

Thank you for your response.

Th Gateway does reference the correct Device Pool. The Device Pool listed the CM Group and the CM Group does list both CM.

How will h225 timeout tcp establish 3 help? Is this necessary for redundant dial peers?

The CCM service is running on both.

Hall of Fame Super Silver

Re: No Redundancy for Inbound Calls

That's the timout the GW uses between rolling between the dial-peers. Yes, you will need it.

Chris

New Member

Re: No Redundancy for Inbound Calls

I mis-understood. I thought the h225 timeout tcp establish 3 was supposed to be placed in the dial peer.

Upon further investigation we already have the router configured with

voice class h323 1

h225 timeout tcp establish 3

I read that "Run H.225D On Every Node" was supposed to be checked within the CM configuration for the gateway. I checked, but couldn't find this option. Any other suggestions.

Also...the primary dial peer is already set to route to the subscriber. The PUB. is secondary. However, my routing problem only occurs when teh PUB is down. I would think that with this config, calls should be routed when the PUB is down.

Hall of Fame Super Silver

Re: No Redundancy for Inbound Calls

Make sure that the replication between the CCMs is working. Look at the "debug isdn q931" logs of the behavior as well as CCM trace file.

Chris

New Member

Re: No Redundancy for Inbound Calls

1. Are you sure that when the primary is up that the calls are actually being routed through the Sub? Or is that always failing and the calls are actually going to the Pub? Remove the second dial-peer to the Pub and see if it still works.

2. Are you callmanagers co-located with the gateway?

3. Are you sure there is no MGCP on that gateway and those dial-peers are not just for mgcp fallback? What is the output for "show ccm-manager"?

I'd recommend you post more of your config.

New Member

Re: No Redundancy for Inbound Calls

I removed the PUB dial peer and tested OK. I put the PUB dial peer back in and removed the SUB dial peer. Both tested successfully.

Our Call Managers are co-located and plugged into the same switch.

We do not have MGCP. I am sure. Our 3660 does not recognize the show ccm-manager command. We are running IOS 12.2(12a)

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