# 31530: DNS Resolution Error

Log Level: ERROR

## Description

This indicates that the Voice client could not connect to the server.

### Possible causes

* Your network is restrictive or uses a VPN, and ICE gathering cannot reach Twilio from all available interfaces.
* Your firewall blocks the outgoing `UDP` traffic required for Twilio Voice media, or it does not allow the Twilio signaling and media destinations your SDK needs.
* You are connecting from a restricted network without providing ICE servers from Twilio Network Traversal Service.

### Possible solutions

* Enable `enableIceGatheringOnAnyAddressPorts` in `ConnectOptions` so ICE candidates are gathered from all available interfaces on Android or iOS.
* Provide ICE servers from Twilio Network Traversal Service through `ConnectOptions` or `AcceptOptions` when your network requires `TURN`.
* Allow outgoing `TCP` and `UDP` traffic to Twilio's signaling and media infrastructure, or use `TURN` over `TCP` or `TLS` if `UDP` is restricted.

#### Additional resources

* [Voice SDKs Network Connectivity Requirements](/docs/voice/sdks/network-connectivity-requirements)
* [Voice Mobile SDKs: Best Practices](/docs/voice/sdks/mobile-best-practices)