# Firewall Problems

Source: https://developer.avalara.com/products/ecm/integration-guides/document-management/bhl7365110276237/

Guide: Exemption Certificate Management (ECM)

# Firewall Problems

Resolve issues connecting to AvaTax caused by firewall restrictions.

## What you see or experience

-   You can’t connect to AvaTax from your network or integration.
-   Requests to AvaTax exceed the time limit or cannot reach the server.
-   Connections work intermittently or stop after network changes.

## Why this happened

Your firewall is blocking AvaTax traffic. AvaTax uses dynamic IP addressesthat change regularly, so filtering by individual IP addresses can prevent propercommunication.

## What helps

Steps

Try the following:

-   Enable access to all IP addresses identified by these DNSnames:
    -   Sandbox environment: [https://sandbox-rest.avatax.com](https://sandbox-rest.avatax.com)
    -   Production environment: [https://rest.avatax.com](https://rest.avatax.com)
-   Avoid filtering traffic by specific IP addresses, as AvaTaxdoesn’t support that method.