Issue
Cause
Solution
Pre-conditions for all issues below:

The network DHCP server is already set to use an efficient DNS server, like Google's DNS, and there are no other network issues.
    
   
Running a VoIP/Soak Test with more than 1 G729 line results in extreme packet loss and delay. Running an early release (unstable) SonicWall firmware version.
  1. Go to System > Status > Write down the Fimware Version number.
  • Confirm that you are running the latest stable version and not an early release firmware.
    • Running early release firmwares is known to cause unexpected call quality problems and phone feature failures.
    • If you are not sure, go to www.mysonicwall.com and login to your My SonicWall account to verify.
    • If you are running an old firmware or an early release firmware, call SonicWall to update to latest stable version of the SonicWall firmware or have your IT upgrade the SonicWall firmware. 
Multiple potential symptoms:
  • Just one phone shows URL calling is disabled, cannot register, but can make outbound calls.  Inbound calls fail to voicemail intermittently or frequently.
  • It is extremely slow loading the web UI on one or more Polycom phones on the network.
  • All phone logs show DNS lookup errors, even though the phones show they are using an efficient DNS, like Google's DNS.
Redundant DSCP setting in the firewall rules that were configured for the phones.
  1. Login to the SonicWall.
  2. Go to Firewall > Access Rules.
  3. Modify each phone rule as shown in the images below.
    1. The 3 phone rules that need this are:
      • WAN to LAN.
      • LAN to WAN.
      • WAN to WAN. 
     
    
    
Pinging the private IP of the SonicWall from a computer connected to the SonicWall shows intermittent spikes in delay. 

The typical response time should be 1ms or 2ms at the most.

It is a critical problem when the delay spikes over 50ms to 100ms or higher in extreme cases.

It will causes audio quality problems, frequent fax failures, and loss of phone/fax device registration.
SonicWall firrmware bug
  1. Go to System > Status > Write down the Fimware Version number.
  2. Confirm that the customer is running the latest stable version and not an early release firmware.
  3. Running early release firmwares is known to cause unexpected call quality problems and phone feature failures.
  4. If you are not sure, got to www.mysonicwall.com and login to your My SonicWall account to verify.
  5. If you are running an old firmware or an early release firmware, advise the customer to call SonicWall to update to latest stable version of the SonicWall firmware or have their IT upgrade the SonicWall firmware.