Hi Mohammed and thank you very much for your answer.
Differently as I've said above, all SIP phone are impacted from my issue.
So, when connection to the CUCM is broken, all SIP phone correctly register on the SRST gateway version 15.4(3)M2, but when communication with CUCM go up again no one phone reconnect to the CUCM. To force that I need to remove "voice register global" command from the router. After about 2 minutes phones come back to the CUCM.
Only SIP phone are affected from this, phone used in my environment are:
7821 (sip78xx.10-2-1-12SR1-4)
9951 (sip9951.9-4-2-13)
ATA190 (1.1.2 (005) Feb 6 2015)
Configuration of the SRST gateway are:
!
voice service voip
allow-connections h323 to h323
allow-connections h323 to sip
allow-connections sip to h323
allow-connections sip to sip
supplementary-service h450.12
fax protocol t38 version 0 ls-redundancy 0 hs-redundancy 0 fallback none
modem passthrough nse codec g711ulaw
h323
sip
bind control source-interface GigabitEthernet0/1.20
bind media source-interface GigabitEthernet0/1.20
registrar server expires max 600 min 60
no silent-discard untrusted
!
!
voice register global
mode srst
timeouts interdigit 7
system message Systema SRST Attivo
max-dn 116
max-pool 58
!
voice register pool 1
registration-timer max 120 min 60
id network 192.168.101.0 mask 255.255.255.0
dtmf-relay rtp-nte sip-notify
voice-class codec 1
!
sip-ua
