To meet PCI DSS Requirement 1.2.1, an entity may install a network firewall between the CDE and corporate network to ensure only designated systems in the corporate network can communicate, via approved ports, to systems in the CDE. This is an example of:

Key PCI DSS Pillars (12 Requirements Summary) Build & Maintain a Secure Network: Install firewalls to protect data and change vendor-supplied default passwords. Protect Cardholder Data: Encrypt stored cardholder data and protect data during transmission over public networks. Maintain Vulnerability Management: Use and regularly update anti-virus software and develop secure systems. Implement Strong Access Control: Restrict data access to "need-to-know," assign unique IDs to each person, and restrict physical access. Regularly Monitor & Test: Track all access to network resources and test... Show more

Key PCI DSS Pillars (12 Requirements Summary)
Build & Maintain a Secure Network: Install firewalls to protect data and change vendor-supplied default passwords.
Protect Cardholder Data: Encrypt stored cardholder data and protect data during transmission over public networks.
Maintain Vulnerability Management: Use and regularly update anti-virus software and develop secure systems.
Implement Strong Access Control: Restrict data access to "need-to-know," assign unique IDs to each person, and restrict physical access.
Regularly Monitor & Test: Track all access to network resources and test security systems regularly.
Maintain Information Security Policy: Maintain a policy that addresses information security for all personnel. 

Steps to Compliance
Define Scope: Identify all systems that handle card data.
Assess: Analyze IT systems for vulnerabilities.
Remediate: Fix vulnerabilities and tighten security.
Report: Submit compliance reports (Attestation of Compliance). 

Common Pitfalls & Tips
Never store prohibited data: Avoid storing Sensitive Authentication Data (SAD) like full magnetic stripe data or CVV codes after authorization.
Use Tokenization: Replace sensitive data with tokens to reduce compliance scope.
Segment Networks: Isolate the Cardholder Data Environment (CDE) from public-facing systems (like guest Wi-Fi) to limit risk. 

Non-compliance can result in monthly fines, increased transaction fees, and legal liability in the event of a data breach.

Also: Introduction to PCI DSS 

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