I recently upgraded 76 MX (65/84/Z3) to the latest code, 14.39.
I am getting random reports of phone calls dropping after 30-60 seconds and one report of calls not going through when dialed. We have the SPA525G1/2 phones and a hosted VoIP service via a Metaswitch provider. *VoIP vendor recently upgraded their system also.
Once we reset the phone (power off/on) the problem goes away. We have one where the problem returned.
Switches are primarily MS120-24P.
I have not been ale to capture any of the drops to attempt to breakdown the connection data.
Does anyone have thoughts on what could be going on here?
L3 outbound rules to the provider's IPs
Traffic shaping of the data to the provider's IPs
In my experience I have not had to implement the Voice VLAN, but its worth trying if the first 2 don't resolve the issue.
Another place to check is with the provider. usually they have QoS team that can look at the details of the calls and see if their platform is dropping the call. If possible you could try the results on a softphone to see if you get the same issues.
@Dennis_S Given both you and your provider have performed upgrades you are going to have fun working this out, can you roll back the firmware on some of the devices and see if the problem resolves itself?
If it goes away after downgrading firmware then its a call to support, if not its a call to your VOIP provider.
To answer a few of the replies... I have both voice VLAN and QoS with no changes to them other than the mentioned OS upgrade.
I have now found that the UDP call is being dropped by the carrier after it does not receive the expected response from the phone during a call.
Changes on a test users phone: We change a single phone to use TCP vs UDP and will monitor the phone activity.
>We change a single phone to use TCP vs UDP
We go a step further and only use SIP/TLS. TCP lets the firewall know when a stream actually starts and stops, and encrypting it prevents anything trying to do anything tricky with application aware NAT.