This was a very interesting scenario I came across for this customer where these two phones were not ringing at all. Any incoming call and they would just flash. No Ringtone.

I confirmed that the phones were working fine few days back but then suddenly started just flashing. One other phone in the same group was working fine. I matched the configuration of all three phones and they were all same. I know that the only way you can change the ring settings from CLI is from the button command.If you are using ‘:’ then that means Ring. Taken from Cisco as follows:

button button-number {separator} dn-tag [,dn-tag…] [button-number{x}overlay-button-number] [button-number…]

:  (colon)—Normal ring. For incoming calls on this extension, the phone produces audible ringing, a flashing icon in the phone display, and a flashing red light on the handset. On the Cisco IP Phone 7914 Expansion Module, a flashing yellow light also accompanies incoming calls.

•b—Beep but no ring. Audible ring is suppressed for incoming calls, but call-waiting beeps are allowed. Visible cues are the same as those described for a normal ring.

•c—Call waiting. Provides call waiting for secondary calls to an overlaid ephone-dn. See also the o keyword.

•f—Feature ring. Differentiates incoming calls on a special line from incoming calls on other lines on the phone. The feature-ring cadence is a triple pulse, as opposed to a single pulse for normal internal calls and a double pulse for normal external calls.

First I thought may be they are getting flashing only on shared lines but confirmed it was the same flashing if someone dial their primary number as well. Configuration of ephone-dn and ephone was similar to this:

ephone-dn  17  octo-line
number 2920
pickup-group 1
label Nicky Brian (2920)
name Nicky Brian
call-forward busy 8005
call-forward noan 8005 timeout 10
corlist incoming User-international
!

ephone  20
mac-address 0023.3XXX.XXXX
ephone-template 1
username “nbri” password welcome
type 7965 addon 1 7916-24
keep-conference endcall
button  1:17 2:187 3s186 4:180
no button  5:182 6:185 7s1 8s2
button  5:181 6:185 7s1 8s2
button  9s3 10s4 11s6 12s8
button  13s10 14s11 15s13 16s14
button  18s28 19s15 20s20 21s37
button  22s27 23s12 24s7 25s36
button  26s29 27s9
!
!

This doesn’t tell me why phones are not ringing. Configuration looks absolutely correct.

Then I decided to check the ephone configuration by running the command ‘sh ephone‘. This customer have quite a few phones with expansion modules so I had to be careful I am looking at right ephones.

This is what I found from one of the ephone which was just flashing.

ephone-20[19] Mac:0023.XXXX.XXXX TCP socket:[13] activeLine:0 whisperLine:0 REGISTERED in SCCP ver 17/12 max_streams=5
mediaActive:0 whisper_mediaActive:0 startMedia:0 offhook:0 ringing:0 reset:0 reset_sent:0 paging 0 debug:0 caps:9 privacy:0
IP:10.60.6.X 12386 7965  sub=1 keepalive 3350 max_line 30 available_line 30 DnD
Phone reports 30 Available Lines
button 1: dn 17 number 2920 CH1   IDLE         CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         shared
button 2: dn 187 number 8802 CH1   IDLE         CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         shared
button 3: dn 186 number 8803 CH1   IDLE         mwi silent-ring shared
button 4: dn 180 number 8005 CH1   IDLE         CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         shared
button 5: dn 181 number 8806 CH1   IDLE         CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         shared
button 6: dn 185 number 8804 CH1   IDLE         CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         shared
button 7: dn 1  number 2904 CH1   IDLE         CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         silent-ring shared
button 8: dn 2  number 2905 CH1   IDLE         CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         mwi silent-ring shared
button 9: dn 3  number 2906 CH1   CONNECTED    CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         silent-ring shared
button 10: dn 4  number 2907 CH1   IDLE         CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         mwi silent-ring shared
button 11: dn 6  number 2909 CH1   IDLE         CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         silent-ring shared
button 12: dn 8  number 2911 CH1   IDLE         CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         mwi silent-ring shared
button 13: dn 10 number 2913 CH1   IDLE         CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6   IDLE         CH7   IDLE         CH8   IDLE         silent-ring shared
button 14: dn 11 number 2914 CH1   CONNECTED    CH2   IDLE         CH3   IDLE         CH4   IDLE         CH5   IDLE         CH6

Carefully look at the above output and I am sure you will know why it was just flashing and not ringing.

The phone had DND enabled!