--- title: "Network System Check Failed: What to Do Next" description: Follow the steps below to troubleshoot if you have failed the Network System Check --- [Skip to content](https://kb.bigmarker.com/knowledge/i-failed-the-network-system-check#main-content) English Show submenu for translations [![Size=36px, Style=On-light, Brand=BigMarker-1](https://kb.bigmarker.com/hs-fs/hubfs/Size=36px%2c%20Style=On-light%2c%20Brand=BigMarker-1.png?width=171&height=36&name=Size=36px%2c%20Style=On-light%2c%20Brand=BigMarker-1.png)](https://www.bigmarker.com/) Open main navigation Close main navigation - English Show submenu for translations Welcome to the BigMarker Knowledge Base! - There are no suggestions because the search field is empty. 1. [Knowledge Base](https://kb.bigmarker.com/knowledge?hsLang=en) 2. [Getting Started](https://kb.bigmarker.com/knowledge/getting-started?hsLang=en) 3. [Network and internet troubleshooting](https://kb.bigmarker.com/knowledge/getting-started?hsLang=en#network-and-internet-troubleshooting) # Network System Check Failed: What to Do Next ## Follow the steps below to troubleshoot if you have failed the Network System Check If you are trying to connect to a webinar from work, a school or religious organization, you may run into a Firewall issue. If have a network Firewall enabled, you may see a black video screen or a **"Connection Can't Be Established"** warning. If possible, please contact your IT department and have them open the necessary Ports *(see below)*.   **Minimum Requirement**: Assumed by default is that TCP ports 80 and 443 are open. Some firewall rules only allow for TCP traffic over port 443, make sure that **all traffic** can pass over this port. If you continue to experience issues, you may need to follow the rest of the rules below. **Best Experience**: In addition to the minimum requirements being met, we recommend that UDP ports 1025 - 65535 be open. **More info: **Our streaming server IP addresses change dynamically and can be any IP address, so you cannot allowlist an IP address range. If you are looking to add our domain to be allowed in your firewall, the easiest thing to do is to allow traffic from all [bigmarker.com](http://bigmarker.com/) servers with \*.[bigmarker.com](http://bigmarker.com/) domain.  **Explicit Firewall rules for your IT department:** 443/tcp ALLOW \*.bigmarker.com 80/tcp ALLOW \*.bigmarker.com 80/udp ALLOW \*.bigmarker.com 53/udp ALLOW \*.bigmarker.com 443/tcp (v6) ALLOW \*.bigmarker.com (v6) 80/tcp (v6) ALLOW \*.bigmarker.com (v6) 53/udp (v6) ALLOW \*.bigmarker.com (v6) 53/udp ALLOW OUT \*.bigmarker.com 80/tcp ALLOW OUT \*.bigmarker.com 443/tcp ALLOW OUT \*.bigmarker.com 443/udp ALLOW OUT \*.bigmarker.com 53/udp (v6) ALLOW OUT \*.bigmarker.com (v6) 80/tcp (v6) ALLOW OUT \*.bigmarker.com (v6) 443/tcp (v6) ALLOW OUT \*.bigmarker.com(v6) 443/udp (v6) ALLOW OUT \*.bigmarker.com (v6) If this does not work, have your IT department email [support@bigmarker.com](mailto:support@bigmarker.com) **Troubleshooting tip**: If you do not believe you are behind a firewall, but are failing the firewall test, please check to see if Stealth Mode is enabled in **AdGuard**.  BigMarker's website can't detect your firewall settings with this enabled. After disabling Stealth Mode, you should pass the Network Firewall check. Similarly, if you have **Kaspersky** enabled, please disable it.    - [Getting Started](https://kb.bigmarker.com/knowledge/getting-started?hsLang=en#main-content) - [BigMarker Basics](https://kb.bigmarker.com/knowledge/getting-started?hsLang=en#bigmarker-basics) - [Intro to presenting](https://kb.bigmarker.com/knowledge/getting-started?hsLang=en#intro-to-presenting) - [Basics of the attendee experience](https://kb.bigmarker.com/knowledge/getting-started?hsLang=en#basics-of-the-attendee-experience) - [BigMarker Troubleshooting](https://kb.bigmarker.com/knowledge/getting-started?hsLang=en#bigmarker-troubleshooting) - [Hardware and Device Troubleshooting](https://kb.bigmarker.com/knowledge/getting-started?hsLang=en#hardware-and-device-troubleshooting) - [Network and internet troubleshooting](https://kb.bigmarker.com/knowledge/getting-started?hsLang=en#network-and-internet-troubleshooting) - [Home, Channel & Profile Settings](https://kb.bigmarker.com/knowledge/getting-started?hsLang=en#home-channel-profile-settings) - [Webinars and Series](https://kb.bigmarker.com/knowledge/webinars-and-series?hsLang=en#main-content) - [Creation & Setup](https://kb.bigmarker.com/knowledge/webinars-and-series?hsLang=en#creation-setup) - [Advanced Settings](https://kb.bigmarker.com/knowledge/webinars-and-series?hsLang=en#advanced-settings) - [Surveys, Stats & Certificates](https://kb.bigmarker.com/knowledge/webinars-and-series?hsLang=en#surveys-stats-certificates) - [On-demand Webinars & Video](https://kb.bigmarker.com/knowledge/webinars-and-series?hsLang=en#on-demand-webinars-video) - [Registration](https://kb.bigmarker.com/knowledge/webinars-and-series?hsLang=en#registration) - [Emails & Invitations](https://kb.bigmarker.com/knowledge/webinars-and-series?hsLang=en#emails-invitations) - [Attendee Experience](https://kb.bigmarker.com/knowledge/webinars-and-series?hsLang=en#attendee-experience) - [Design](https://kb.bigmarker.com/knowledge/webinars-and-series?hsLang=en#design) - [Promotion & Sharing](https://kb.bigmarker.com/knowledge/webinars-and-series?hsLang=en#promotion-sharing) - [Virtual & Hybrid Events](https://kb.bigmarker.com/knowledge/virtual-hybrid-events?hsLang=en#main-content) - [Event Setup](https://kb.bigmarker.com/knowledge/virtual-hybrid-events?hsLang=en#event-setup) - [Virtual Venue](https://kb.bigmarker.com/knowledge/virtual-hybrid-events?hsLang=en#virtual-venue) - [Registration](https://kb.bigmarker.com/knowledge/virtual-hybrid-events?hsLang=en#registration) - [Analytics/Integrations](https://kb.bigmarker.com/knowledge/virtual-hybrid-events?hsLang=en#analytics-integrations) - [Sessions and user journeys](https://kb.bigmarker.com/knowledge/virtual-hybrid-events?hsLang=en#sessions-and-user-journeys) - [Design](https://kb.bigmarker.com/knowledge/virtual-hybrid-events?hsLang=en#design) - [Sponsors & Networking](https://kb.bigmarker.com/knowledge/virtual-hybrid-events?hsLang=en#sponsors-networking) - [Hybrid Settings & Streaming](https://kb.bigmarker.com/knowledge/virtual-hybrid-events?hsLang=en#hybrid-settings-streaming) - [Presenter Capabilities](https://kb.bigmarker.com/knowledge/presenter-capabilities?hsLang=en#main-content) - [Using the Studio](https://kb.bigmarker.com/knowledge/presenter-capabilities?hsLang=en#using-the-studio) - [Presenter Settings & Permissions](https://kb.bigmarker.com/knowledge/presenter-capabilities?hsLang=en#presenter-settings-permissions) - [Content & Engagement](https://kb.bigmarker.com/knowledge/presenter-capabilities?hsLang=en#content-engagement) - [Integrations](https://kb.bigmarker.com/knowledge/integrations?hsLang=en#main-content) - [Webinar, Series and Event integrations](https://kb.bigmarker.com/knowledge/integrations?hsLang=en#webinar-series-and-event-integrations) - [Channel Integrations](https://kb.bigmarker.com/knowledge/integrations?hsLang=en#channel-integrations) - [In-person events & Mobile Event Apps](https://kb.bigmarker.com/knowledge/in-person-events-mobile-event-apps?hsLang=en#main-content) - [Event Companion App](https://kb.bigmarker.com/knowledge/in-person-events-mobile-event-apps?hsLang=en#event-companion-app) - [Scanner App, QR Codes & Badge Printing](https://kb.bigmarker.com/knowledge/in-person-events-mobile-event-apps?hsLang=en#scanner-app-qr-codes-badge-printing) - [BigMarker AI](https://kb.bigmarker.com/knowledge/bigmarker-ai?hsLang=en) - [Privacy, Security & Policies](https://kb.bigmarker.com/knowledge/privacy-security-policies?hsLang=en) [![Size=36px, Style=On-light, Brand=BigMarker-1](https://kb.bigmarker.com/hs-fs/hubfs/Size=36px%2c%20Style=On-light%2c%20Brand=BigMarker-1.png?width=171&height=36&name=Size=36px%2c%20Style=On-light%2c%20Brand=BigMarker-1.png "Size=36px, Style=On-light, Brand=BigMarker-1")](http://bigmarker.com) © 2010 - 2026 BigMarker. 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