Router Setting Guidelines

Router Setting Guidelines

This article describes the recommended network settings that help ensure your router, firewall, or modem/router combination works properly with PENGUIN service. These adjustments are typically made through your device’s web interface.

After making any changes, restart your network equipment to ensure the new settings take effect.

Helpful Tools: These utilities can quickly detect SIP ALG and NAT timeout issues, two of the most common causes of call failures, one-way audio, or phones losing registration.
SIP ALG / SIP Transformations SIP ALG modifies VoIP traffic, often breaking phone registration, causing no-audio calls, or disconnects.

PENGUIN service does not require SIP ALG, and we strongly recommend disabling:
  • SIP ALG
  • SIP Transformations
  • VoIP Application Layer Gateways
  • SIP Inspection (Cisco)
Cisco devices may require the commands:
no inspect sip or no fixup protocol sip 5060.
VoIP-optimized router features Some routers include proprietary VoIP optimization features that interfere with PENGUIN’s cloud platform.

These features are unnecessary and may cause:
  • Phones losing registration
  • Random call drops
  • Delayed or missing audio
Disable these if available on your router.
SPI / DoS Protection Stateful Packet Inspection (SPI) and Denial-of-Service protection can incorrectly flag legitimate phone traffic as an attack.

As the number of phones increases, these router protections may begin blocking PENGUIN traffic.

If your router allows it:
  • Disable SPI/DoS protection entirely, or
  • Increase connection limits to prevent blocking.
SIP, UDP & RTP Protocol Handling PENGUIN service uses SIP for signaling and RTP for audio. Restrictive firewall rules can prevent calls from completing or cause one-way audio.

Key requirements:
  • No outbound restrictions for SIP/UDP traffic.
  • UDP session timeout ≥ 30 seconds.
  • RTP audio ports 20000–30000 must be allowed.
Blocking RTP ports will result in one-way or no audio.
Double-NAT (Double-Routing) VoIP traffic does not handle multiple layers of NAT well. If your ISP provides a modem/router combo plus you have your own router, you may be double-NATed.

Recommended:
  • Bridge the ISP modem/router (ISP must assist)
  • OR place your router inside the modem’s DMZ (may not always work)
Port forwarding is not recommended. PENGUIN phones establish secure outbound connections dynamically—no forwarding rules are required. 

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