Firewall: Definition & role for cloud telephony | NFON Knowledgebase UK [Contact](# "Contact") ![](/web-assets/f/290788/40x40/d98615a3ea/nfon-sales-contact.svg) Sales & General * [Talk to Sales](tel:+443303838000) * [Write to us](/gb/request-information) Search * [![Products](https://a.storyblok.com/f/290788/40x40/539cd331b9/nfon-products.svg) Products](#) Call & Work ![AI icon](/assets/ai_icon.webp) + [Cloud Telephony](/gb/products/cloud-telephony/) + [SIP Trunk](/gb/products/enablement/) + [Devices](/gb/products/devices) Build & Automate ![AI icon](/assets/ai_icon.webp) + [Assistants](/gb/products/ai/assistants) + [Bots](/gb/products/ai/bots) + [AI Agent Studio](/gb/products/ai/agent-studio) Engage & Support ![AI icon](/assets/ai_icon.webp) + [Contact Center](/gb/products/customer-contact/) Integrations & Add ons + [Integrations & Add ons](/gb/integrations/) * [![Solutions](https://a.storyblok.com/f/290788/40x40/da156cbbb8/nfon-solutions-industries.svg) Solutions](#) Industries + [Health & Wellness](/gb/solutions/health-wellness) + [Retail & E-Commerce](/gb/solutions/retail) + [Finance & Legal](/gb/solutions/finance-insurance) + [Travel & Hospitality](/gb/solutions/hospitality) + [Public Sector](/gb/solutions/public-sector) + [Energy](/gb/solutions/energy) Success stories + [Customer Stories](/gb/customer-stories/) * [![Partnerships](https://a.storyblok.com/f/290788/36x36/7bd105c67d/nfon-partner.svg) Partnerships](#) Partner with NFON + [Partner](/gb/partner/become-partner) + [NGAGE](/gb/partner/partner-programme) Partner Portal + [Partner Portal](https://partners.nfon.com/) * [![Help Center](https://a.storyblok.com/f/290788/40x40/d01fbb4f30/help-nfon.svg) Help Center](/gb/help-centre) * [Login](https://start.cloudya.com/ "Login") * United Kingdom + [International](/en) + [Deutschland](/de) + [España](/es) + [France](/fr) + [Italia](/it) + [Österreich](/at) + [Polska](/pl) + [Portugal](/pt) + [United Kingdom](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/firewall) [![NFON Logo](/assets/logo-nfon.svg)](/gb/ "NFON Home") * [Products](#) ![](/web-assets/f/290788/36x36/a9f3ceed6f/nfon-call-work.svg) Call & Work ![AI icon](/assets/ai_icon.webp) Seamless communication ![](/web-assets/f/290788/36x36/d03c61cf40/nfon-build-automate.svg) Build & Automate ![AI icon](/assets/ai_icon.webp) AI Automation ![](/web-assets/f/290788/36x36/106823b73b/nfon-engage-support.svg) Engage & Support ![AI icon](/assets/ai_icon.webp) Omnichannel support ![](/web-assets/f/290788/36x36/50b60f5411/nfon-integrations-add-ons.svg) Integrations & Add ons Connect Teams & CRMs + [![](/images/products-call-work-cloudteleophny-navbar-int_Fjf8b.webp) ### Cloud Telephony ![AI icon](/assets/ai_icon.webp) Seamless cloud telephony for every device. High-fidelity audio with European-grade security.](/gb/products/cloud-telephony/) + [![](/images/products-call-work-siptrunk-navbar-int_ZH5NzW.webp) ### SIP Trunk Secure cloud connectivity for your existing hardware. Scales instantly with your business.](/gb/products/enablement/) + [![](/images/products-call-work-devices-navbar-int_Z2dP6.webp) ### Devices Professional telephones and hardware designed for clear calls and all-day comfort.](/gb/products/devices) + [![](/images/products-build-automate-assistants-navbar-int_2ghUIJ.webp) ### Assistants ![AI icon](/assets/ai_icon.webp) Pre-configured, plug-and-play digital roles like FrontDesk and Workdesk. Ready to deploy instantly with zero coding required.](/gb/products/ai/assistants) + [![](/images/products-build-automate-bots-navbar-int_Z1p57Vm.webp) ### Bots ![AI icon](/assets/ai_icon.webp) Prompt-driven, multi-channel conversational experiences. Automate custom customer journeys across Web Chat, Voice, and Livechat.](/gb/products/ai/bots) + [![A chatbot creation interface is shown with a readiness message, build report, agent prompt details, and created tools list, over a gradient background.](/images/products-build-agent-studio-navbar-int_Z1Y88dE.webp) ### AI Agent Studio ![AI icon](/assets/ai_icon.webp) Simply turn your ideas into AI agents for your business. Describe the task, create a working agent, then optimize it in one workspace.](/gb/products/ai/agent-studio) + [![](/images/products-engage-support-navbar-int_1xyFBE.webp) ### Contact Center ![AI icon](/assets/ai_icon.webp) Omnichannel customer service for modern teams. Manage conversations, automation, AI assistance, and customer context.](/gb/products/customer-contact/) + [![](/images/products-integrations-addons-navbar-int_Z1Ka5ea.webp) ### Integrations & Add ons Expand your capabilities and natively connect your everyday business to keep all workflows unified.](/gb/integrations/) * [Solutions](#) ![](/web-assets/f/290788/40x40/da156cbbb8/nfon-solutions-industries.svg) Industries Tailored solutions ![](/web-assets/f/290788/40x40/155f2a989d/nfon-success.svg) Success stories 54,000+ trust us + [![](/images/solutions-health-wellness-navbar-int_Z15q3kJ.webp) ### Health & Wellness Secure communication for better patient experiences and care delivery.](/gb/solutions/health-wellness) + [![](/images/solutions-retail-ecommerce-navbar-int_zUgjw.webp) ### Retail & E-Commerce Connected communication for modern retail and customer engagement.](/gb/solutions/retail) + [![](/images/solutions-finance-legal-navbar-int_1Dy5Ax.webp) ### Finance & Legal Trusted communication for regulated and security-conscious organizations.](/gb/solutions/finance-insurance) + [![](/images/solutions-hospitality-travel-navbar-int_17WoBe.webp) ### Travel & Hospitality Seamless communication for exceptional guest experiences and service.](/gb/solutions/hospitality) + [![](/images/solutions-publicsector-navbar-int_YyABB.webp) ### Public Sector Reliable communication for responsive public services and citizen support.](/gb/solutions/public-sector) + [![](/images/solutions-energy-navbar_FDoix.webp) ### Energy Reliable communication for responsive customer service, even during outages and peak demand.](/gb/solutions/energy) + [![](/images/solutions-costumerstroy-navbar-int_Z1MdOsM.webp) ### Customer Stories Real-world impact across every industry. Explore how we solve complex communication challenges for Europe’s leading brands.](/gb/customer-stories/) * [Partnerships](#) ![](/web-assets/f/290788/36x36/7bd105c67d/nfon-partner.svg) Partner with NFON Join the NFON network ![](/web-assets/f/290788/36x36/8c5c9a9c78/nfon-partner-portal.svg) Partner Portal Existing partner login + [![](/images/partnerships-partner-navbar-int_ZHYGKx.webp) ### Partner From onboarding to co-branded marketing, we provide the tools you need to win.](/gb/partner/become-partner) + [![](/images/partnerships-ngage-navbar-int_Zs3yY9.webp) ### NGAGE Discover our tiered rewards system designed to help you scale your business and revenue.](/gb/partner/partner-programme) + [![](/images/partnerships-partnerportal-navbar-int_2ki451.webp) ### Partner Portal Access partner tools, deal registration, training resources, and program benefits in one place.](https://partners.nfon.com/) * [Help Center](/gb/help-centre) * Search * [Login](https://start.cloudya.com/ "Login") * gb + [International](/en) + [Deutschland](/de) + [España](/es) + [France](/fr) + [Italia](/it) + [Österreich](/at) + [Polska](/pl) + [Portugal](/pt) + [United Kingdom](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/firewall) * [Contact](#) [Contact](# "Contact") + ![](/web-assets/f/290788/40x40/d98615a3ea/nfon-sales-contact.svg) Sales & General Get in touch with us. ![](/images/getstarted-talktosales-navbar-int_ZMspQ4.webp) ### Talk to Sales Get a free consultation to see how NFON products can meet your needs. [+44 330 383 8000](tel:+443303838000 "+44 330 383 8000") ![](/images/getstarted-writetous-navbar-int_ZY7MOf.webp) ### Write to us Fill out our request form. Our experts will respond as soon as possible. [Write to us](/gb/request-information "Write to us") ### Firewall [The difference between personal firewall and external firewall](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/firewall#section-3) [Basic functions of a firewall](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/firewall#section-4) [Different firewall strategies](/gb/get-started/cloud-telephony/lexicon/knowledge-base-detail/firewall#section-5) # Firewall A firewall protects the local network or local devices from unauthorised connections from the public Internet. It can consist of just software or a combination of software and hardware. The firewall function is able to monitor both incoming and outgoing data traffic and block or allow it as necessary. It captures data between an external (public) and internal (local) network or connection. In a private environment firewall functions are often implemented in the internet access router. However, downstream dedicated devices may also be used. ### The difference between personal firewall and external firewall We generally distinguish between a personal firewall and an external firewall. The personal firewall is running on the actual device being secured. For example, Windows computers have a software-based firewall function which monitors the computer's traffic. An external firewall is not installed on the actual device being secured, but on separate hardware installed between two network segments. It can restrict access between the two networks and is separate from the connected devices. ### Basic functions of a firewall To ensure effective protection, the firewall function is able to analyse data traffic based on destination and originator addresses, ports and protocols. Defined rules only allow certain network packets to pass through the firewall. Important components are a packet filter including port and protocol filter, functions related to network address translation (NAT) and the ability to match packets with different connection statuses (stateful inspection). Logging blocked packets is essential to later analyse these. ### Different firewall strategies Two essential strategies can be used for configuration. One strategy is to first block all traffic and only allow desired connection with rules defined at a later time. The contrary strategy allows all traffic and blocks only undesired connections based on rules. The firewall is often also used as a central endpoint for virtual private networks (VPN connections). These allow devices to establish secured connections to the internal network over the internet. [Back](#) ![NFON Logo](/assets/logo-nfon.svg) News * [Events](https://www.nfon.com/gb/news/events/) * [Press](https://www.nfon.com/gb/news/press/) Customers * [Cloudya Login](https://start.cloudya.com/auth/login) * [Admin Portal](https://admin.nfon.com/) * [NFON Status](https://status.nfon.com/) About NFON * [Corporate](https://corporate.nfon.com/en/) * [Investor Relations](https://corporate.nfon.com/en/investor-relations/ir-at-a-glance/) * [Sustainability & ESG](https://corporate.nfon.com/en/sustainability/) * [Career](https://corporate.nfon.com/en/careers/) Legal * [GTC-SLA](/gb/legal/gtc-sla) * [Legal Notice](/gb/legal/legal-notice) * [Trust Centre](https://www.nfon.com/en/trust-center/) * [Data Protection](/gb/legal/data-protection) * [Cookie Settings](javascript:onclick=UC_UI.showSecondLayer()) © 2026 - NFON | All rights reserved.