Phones do not fallback to Call Manager and stay register with the SRST Gateway

[O.Zang]

Hi Experts,

Please help me solve this issue.

 After losing connection, my phonse goes into SRST mode. The connectivity back to CUCM servers is restored but the phonse stays in SRST mode until a manual reboot is done.

Phones are using sip78xx.11-7-1-17 firmeware.
CUCM version: 11.5.

I opened a TAC case since 13/09/2018 but we still don't found a way to solve the issue.

I was given  78xx.12-1-1ES7 firmeware that i applyed on 2 phones that still stays registered  with the 4321 SRST.

Below is my E-SRST config.

voice service voip
allow-connections h323 to h323
allow-connections h323 to sip
allow-connections sip to h323
allow-connections sip to sip
no supplementary-service sip refer
fax protocol t38 version 0 ls-redundancy 0 hs-redundancy 0 fallback none
h323
sip
bind control source-interface GigabitEthernet0/0/0.1
bind media source-interface GigabitEthernet0/0/0.1
registrar server
!
voice class codec 1
codec preference 1 g711ulaw
codec preference 2 g729r8
codec preference 3 g711alaw
!
!
!
!
voice iec syslog
!
voice register global
mode esrst
no allow-hash-in-dn
system message "MODE SRST"
max-dn 20
max-pool 20
!
voice register pool 1
id network 10.163.6.16 mask 255.255.255.240
dtmf-relay rtp-nte sip-notify
voice-class codec 1
no vad
!
!
!
!

Thanks In advance for your Help.

Regards,

Zanga

[R0g22]

Are you using FQDN for your CUCM servers ? I remember a couple of defects that affect some SIP Phones not able to register back to CUCM post SRST. I will add them here if I find them.

[O.Zang]

Hi Nipun ,

I am using Ip address rather than FQDN for my CUCM server. 

Thank in advance for the file that you are going to share.

Regard,

Zanga

[evlaa1990]

I think this is set under the device pool within CUCM 'Connection Monitor Duration'. Default is 120 seconds - maybe this has been changed?

[O.Zang]

Hello evlaa1990 ,

I have changed this value. but still not able to automaticaly fallback.

[O.Zang]

Hi Nipun Singh Raghav,

I double check my cucm servers and found that the Publisher is using a FQDN buit the subscriber has an IP address.

Ip phones on branches site have to register first with the sub surver.

Zanga

[O.Zang]

Dear Experts

Any idea about solving this issue ?

I have captured trafic from the Ip phone that is showing that the phone is sending TCP connection to the CUCM.

But still not able to register back without a reboot.

Regards

Zanga

[R0g22]

Yeah, your issue is very similar to a defect that I remember but like I said can't find it anymore. Take a look at this and see if any of these checks all the reqs -

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCus18070/?reffering_site=dumpcr

[R0g22]

A phone log would show what are the phones doing to really understand if it is due to the FQDN or is it just a TCP.

[O.Zang]

A TAC ngineer said that, this can be due to the Network /firewall.

but there is nothing block between the phone and the CUCM server.

I think if this was the firewall blocking the traffic, phone may not register back event if we reboot the phone.

Regard,

Zanga

[O.Zang]

Hello Expert,

I used cucm sub for Tshoot purpose. 

I got the CUCM sub and the SRST gateway directly connected.

Here is what i did: phone, CUCM sub and srst gateway  connected on the same switch. SRST gateway and CUCM Sub share the Same network.  This what to isolate the the firewall , routers and other core switches.

With that in place the phone can fallback automatically to the cucm when the wan connectivity is restored.

I have checked the network config and can't see any configuration that coul prevent the phone from registering back with cucm.

Any idea on what can block the phone from falling back to cucm when traversing the other components of the network ?

PS: an reboot makes the phone register tho cucm.

Regards,

Zanga