1. Disable SIP ALG. 
    • This is the most important and critical setting to change.
    • This is also known as SIP Transformations
    • If you don't have an option, call Intermedia Cloud Voice Technicial Support to use our SIP ALG Detector Tools to verify is a device has SIP ALG or not.
          
  2. Ensure the router/firewall does not block the phones' NAT Binding/Keep-Alive packets that are sent every 15 seconds. 
    • Most routers do not block the phones' Keep-Alive packets by default, but many high-end firewalls, like Barracudas, do.
    • Some firewalls don't have an option to allow the packets, so an alternate solution is to set the phone's UDP session timeout to 300 seconds, since the phones send a SIP packet re-registration request every 5 minutes.
          
  3. Allow phones to connect outbound to Intermedia Cloud Voice servers:
    • Most routers/firewalls allow this by default since the Intermedia phones & other devices initiate the outbound connection to our servers, which isn't a security risk.
    • However, some advanced firewalls/security appliances and highly-restricted-networks may require manually creating rules to do this to the addresses below.
    • See the article Network Ports and Protocols for HPBX Phones (After 3/2/14) for more details.
      • RTP (Call Audio) & SBC Servers:
        • 64.28.114.0/24
        • 64.28.116.0/24
        • 64.28.124.0/24
        • 64.28.123.0/24
      • SIP Registration Server Main:
        • 64.28.113.10
        • 64.28.119.10 (for accounts created after 5/6/15)
      • Phone Configuration Servers:
        • 64.28.112.148
        • 64.28.115.146
      • Phone DNS & Time Servers:
        • 64.28.112.157
        • 64.28.115.137
        • 64.28.126.9
      • WAN Ping Test Server:
        • 64.28.122.110
        • 64.28.121.110
      • VoIP/Soak Tester Server: 64.28.122.103 and 64.28.121.101
      • Legacy Vertical Phone System Server Addresses:
        • SVDNS: 64.28.126.29
        • PTS: 64.28.115.150
              
  4. This step is only needed if you have or plan to purchase Polycom phones:
    • Disable DNS proxy/relay on all DHCP and DNS servers on your network
    • Set the DHCP DNS servers (DHCP option 6) to a set of efficient DNS server addresses such as:
      • Google's DNS:
        • 8.8.8.8
        • 8.8.4.4
      • Or OpenDNS:
        • 208.67.222.222
        • 208.67.220.220
    • The reason the DNS servers above need to be used is because many ISP or LAN DNS servers take too long to relay DNS lookup requests, causing the Polycom phones intermittently lose registration. 
    • If you must use your own private DNS server addresses, then you will need to setup Stub DNS Forward Zones on your own private DNS server, like a Windows Server, that forwards all requests for *.Intermedia.net or *.accessline.com directly to our DNS servers below:
      • accessline.com DNS Servers:
        • 64.28.126.9
        • 64.28.115.137
        • 64.28.112.157
      • Intermedia.net DNS Servers:
        • 64.78.57.46
        • 162.244.196.45
        • 64.78.22.187
        • 206.225.164.198
              
  5. The phones and other Intermedia devices must be behind a NAT-enabled firewall and must get their private IP addresses via DHCP.
    • The phones and other VoIP devices cannot be configured with static private IP addresses or public IP addresses.
          
  6. This is needed for call quality monitoring and troubleshooting purposes:
    • Allow WAN pings from our Call Quality Monitoring Servers 64.28.122.110 and 64.28.121.110
           
  7. Strongly Recommended:
    • Setup Bandwidth Management/Rate Control/Traffic Shaping to reserve the exact amount of bandwidth your phones need at all times.

Disclaimer: The requirements below will not guarantee that the router will work properly, but they should get most routers working.  Outdated and/or unstable router firmware and other network issues can cause unexpected phone issues that changing the settings above cannot resolve.