What two problems do Network Address Translations (NATs) introduce into VoIP networks? (Choose two.)
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Network Address Translation (NAT) is a mechanism that enables multiple devices on a private network to share a single IP address when connecting to the Internet. NATs translate private IP addresses to a public IP address, allowing traffic to flow between the private and public network.
However, NATs can introduce problems in VoIP networks, particularly in scenarios where VoIP traffic traverses a NAT device. The following are two common problems associated with NATs in VoIP networks:
NATs block unsolicited incoming signaling and media: NATs typically block unsolicited incoming traffic, including signaling and media packets that are not in response to a previous outgoing packet. This can cause issues in VoIP networks because incoming calls may not be received, or incoming media may be blocked. To overcome this problem, a technique called "hole punching" is used, where the NAT device is configured to allow incoming traffic to specific ports and IP addresses associated with VoIP communications.
NATs pinholes expire after a configurable time: NATs create temporary connections, called pinholes, that enable incoming traffic to pass through the NAT device. However, these pinholes expire after a configurable time, which can result in the loss of connectivity for VoIP devices. To prevent this from happening, VoIP devices need to be configured to periodically send keep-alive messages to maintain the NAT pinhole.
In conclusion, NAT devices can introduce problems in VoIP networks, particularly in scenarios where VoIP traffic traverses a NAT device. The two common problems associated with NATs in VoIP networks are blocking unsolicited incoming signaling and media and the expiration of NAT pinholes after a configurable time. It is important to configure VoIP devices to overcome these issues and ensure reliable connectivity in VoIP networks.