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New Member

CM Fallback

We have 6 sites all connected over an IP MPLS netwok.  Chicago is the Host with Call Manager 6.1.  All sites have 2821 H.323 Gateways.  All sites have the same running config on the Gateway for QOS.  2 our sites keep having issues with phones going into CM Fallback Service.  It happens intermittenly and the phones are in CM Fallback Service no longer than a couple of minutes.  When contacting the ITSP the circuit is up and stable.  Could we be experiencing a QOS issue or do I need to up the time on the Keep-alives on the Gateway?  Currently set to default.

just incase:

call-manager-fallback
max-conferences 4 gain -6
transfer-system full-consult
limit-dn 7940 2
limit-dn 7960 2
ip source-address 10.220.1.2 port 2000
max-ephones 50
max-dn 48
translate calling 10
call-forward busy 0800
call-forward noan 0800 timeout 15

Thanks,

Jaime

4 REPLIES

Re: CM Fallback

The phones will register with the SRST router if they lose connectivity to the CUCM servers at the central site.

By default the phones send TCP keepalives using TCP port 2000 (SCCP) every 30 seconds. If three keepalives are not acknowledged then the phone will register with its SRST router.

The keepalive packets go from the phones to the CUCM servers - there is nothing on the gateway that can help resolve this situation. You could modify the CUCM Station Keepalive Interval service parameter from the default of 30 seconds to a maximum of 1000 seconds but this would mask rather than resolve the problem.

You really need to determine why the keepalives are being lost.

New Member

Re: CM Fallback

I appreciate the info.

What do you think my best bet would be on troubeshooting dropped packets?  I spoke with Telco and of course they state they cannot see anything on their end.  Which perhaps might be.  Could this be a possibly a QOS issue?  Should I start sniffing packets on both ends?  Please advise?

Thanks,

Jaime

Re: CM Fallback

Jaime,

Do you control the MPLS network that runs between sites or are you purchasing bandwidth for your WAN connectivity from a carrier that is providing the MPLS network?

Hailey

New Member

Re: CM Fallback

Hi Hailey,

Yes we just purchased SIP Trunks from an ITSP.  We manage the CER and the provider manages their equipment.  Do you think we might need some fine tuning on the CER and PER?

Thanks,

Jaime

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