Double NAT, or multiple routers on one network, is when two or more Routers’ Network Address Translations (NAT) are placed one after the other. Double NAT is common with computer use and web browsing, but is not recommended for VoIP.
Double NAT (Double Routing) is most common when you connect an additional router to the existing router or gateway your Internet Service Provider gave you.
Here’s an example of a simple network with one gateway (say DSL or Cable modem). The gateway has a public (WAN) IP address and does NAT. All computers that are connected to this gateway get assigned a private IP address. The gateway routes the data from and to the computers connected to it. If you have more than one router, the Network Address Translation is placed one right after another, creating a Double NAT.
This can cause intermittent issues, including:
- One way audio on calls
- Phones dropping registration periodically
- Transfers not completing successfully
- Error messages when dialing a number
- Hunt groups not working properly
- Calls dropping involuntarily