Implementing Geo-Based Access Controls for IKEv2 VPNs is an effective way to reduce attack surface, meet compliance requirements, and tailor access to organizational needs. This article dives into the technical mechanics, design considerations, and practical implementation patterns for enforcing geographic restrictions on IKEv2 (IPsec) VPN connections. It targets site owners, corporate IT teams, and developers who manage or integrate VPN services and need robust, scalable controls.

Why apply geo-based controls to IKEv2 VPNs?

Geo-based access controls allow administrators to allow or deny VPN connections based on the geographic origin of the client IP address. For IKEv2 VPNs, this provides several advantages:

  • Reduced attack surface: Blocking high-risk geographies reduces the pool of potential attackers and automated scans.
  • Compliance and data residency: Enforce access policies that reflect regulatory or contractual restrictions.
  • Operational efficiency: Prioritize capacity and monitoring for expected regions; reduce noise from spam connections.
  • Layered security: Complement multi-factor authentication (MFA), certificate-based authentication, and endpoint posture checks.

Core concepts: how geographic decisions map to IKEv2

Geo-based decisions for IKEv2 are made using the client’s source IP address observed during IKE negotiations. Important technical points to consider:

  • GeoIP accuracy: GeoIP databases map IP ranges to countries/regions; accuracy varies and must be updated regularly.
  • Where to enforce: Decisions can be applied at the VPN gateway, at edge firewalls, at identity providers (IdP), or a combination.
  • Failure modes: Block failures can affect legitimate roaming users (e.g., mobile users tunneling through another country), so handling of false positives is essential.
  • Protocol flow: IKEv2 first performs IKE_AUTH (establishes IKE SA and authenticates) before creating Child SAs for IPsec traffic—geo checks can be applied at IKE phase (rejecting IKE_AUTH) or post-authentication for fine-grained policy.

Enforcement points and trade-offs

Choose enforcement locations based on control granularity, latency, and manageability:

  • Edge firewall or cloud WAF: Quick rejection of disallowed IP ranges before VPN processing; efficient but coarse-grained.
  • VPN gateway (IKE daemon): Apply geo filters during IKE_AUTH. Offers the most precise control, allows authentication and error messaging, but requires integration with GeoIP lookup.
  • Identity layer (RADIUS/Radius server or AuthZ): Enforce geo policy during authorization callbacks; useful in environments using enterprise IdPs.
  • Post-auth context: Use route policies or access-lists on child SAs to restrict allowed subnets after authentication.

Practical implementation with common IKEv2 stacks

Below are approaches for popular implementations: strongSwan (Linux), Windows RRAS, and cloud VPN gateways.

strongSwan (Linux): plugin and ipset approach

strongSwan is widely used for IKEv2 on Linux. Two patterns work well:

  • Pre-check via firewall/iptables + ipset: Maintain an ipset of allowed or blocked countries (derived from GeoIP ranges) and reference that in iptables rules to drop or accept UDP/500/4500 packets before they reach strongSwan.
  • Integration via plugin or script: Use strongSwan’s charon lifecycle hooks to call an external GeoIP check during ike events (e.g., pre_shared_key or cert auth). A script can query a local GeoIP database (MaxMind, IP2Location) and return accept/reject.

Example ipset + iptables snippet (conceptual):

ipset create geo_allowed hash:net
ipset add geo_allowed 203.0.113.0/24

iptables -I INPUT -p udp --dport 500 -m set --match-set geo_allowed src -j ACCEPT
iptables -I INPUT -p udp –dport 500 -j DROP

This short-circuits disallowed sources before engaging the VPN daemon, saving CPU and logging clearer rejections.

Windows Server and RRAS

Windows RRAS does not have native GeoIP filtering for IKE. Typical patterns are:

  • Use Windows Firewall or perimeter appliances (e.g., Azure Network Security Groups) to block IP ranges.
  • Leverage RADIUS authentication policies with custom attributes: a RADIUS proxy can perform GeoIP checks and deny authentication.

Cloud VPN gateways (AWS, Azure, GCP)

Cloud-managed VPN gateways often sit behind cloud firewalls (NSGs, Security Groups, Cloud ACLs). Implement geo-controls at the network ACL level or an upstream firewall appliance. For more refined control, integrate with an on-prem or cloud-based RADIUS or authorization function that inspects the source IP and enforces policies.

GeoIP data: databases and update strategies

Geo-based accuracy depends heavily on the data source and update cadence. Best practices:

  • Use reputable providers: MaxMind GeoIP2 (commercial), or GeoLite2 (free), IP2Location, or commercial feeds with SLA.
  • Automate updates: schedule daily or weekly updates; have an automated process to rebuild ipsets/firewall ACLs from the data.
  • Prefer CIDR lists: transform country allocations into CIDR blocks to use with ipset or firewall rules.
  • Track changes: log diffs and maintain a change window; big changes can otherwise inadvertently block users.

Automating CIDR list generation

Typical flow for a Linux gateway:

  • Download GeoIP CSV/JSON.
  • Parse to extract IP ranges per country.
  • Convert ranges to CIDR (use ipcalc or libraries).
  • Replace ipset contents atomically (create new set, swap, flush old).

Authentication considerations

Geo restrictions are most effective when combined with strong IKEv2 authentication:

  • Certificate-based auth: Trusted client certificates plus geo checks reduce credential-based attacks.
  • RADIUS / EAP: Integrate Geo checks into the RADIUS flow. A RADIUS proxy can return Access-Reject or set an attribute to limit session lifetime if coming from unknown geographies.
  • MFA integration: Combine with MFA for regions that are allowed but considered higher risk.

Policy design: allow-list vs block-list

Decide on an allow-list (default deny) or block-list (default allow) strategy:

  • Allow-list: Only explicitly permitted countries can initiate VPN connections. Stronger security, but risks blocking mobile or traveling users.
  • Block-list: Simpler to maintain when you only want to exclude a small set of high-risk countries. Safer for global workforce access.

For most enterprises with a known user base, an allow-list with exceptions for support workflows is recommended. Always implement a safe bypass mechanism (e.g., secondary VPN endpoint or support ticket process).

Logging, monitoring, and forensics

Visibility is critical for tuning and incident response:

  • Log IKEv2 negotiation attempts and firewall drops with source IP and country tags.
  • Enrich logs with GeoIP metadata at the point of ingestion (SIEM) to reduce later lookup costs.
  • Monitor for repeated hits from blocked geographies—may indicate targeted reconnaissance or botnets.
  • Keep audit trails of GeoIP feed updates and policy changes.

Handling edge cases and mitigation

Prepare for legitimate exceptions and spoofing risks:

  • VPN/proxy hopping: Attackers or even users may route through other jurisdictions. IP-based geo measures cannot prevent this; rely on MFA and certs for strong assurance.
  • Mobile roaming: Implement “prompt for MFA” or temporary allowances when users travel legitimately.
  • False positives: Provide a documented exception process with short-lived allow rules and ticketing integration.
  • IP spoofing attempts: For UDP-based IKE packets, spoofing is possible but IKEv2’s multi-step handshake and crypto prevents session hijack; nonetheless packet source filtering at edge routers helps.

Performance and scaling

Design for performance when handling large GeoIP lists or high connection rates:

  • Use ipset (hash:net) instead of per-rule iptables entries—this scales to thousands of networks with O(1) lookup.
  • Cache GeoIP lookups in memory for repeated source IPs; avoid per-packet DB lookups.
  • Consider distributing enforcement: edge CDN/firewall for coarse blocks, gateway for fine-grained decisions.
  • Benchmark: measure connection setup latency with Geo checks in-line vs pre-filtered at firewall to identify acceptable latencies for your SLAs.

Example architecture patterns

Three common deployment patterns:

  • Edge-first: Cloud/edge firewall enforces country blocks; strongSwan handles authentication. Best for high-volume environments.
  • Gateway-enforced: strongSwan + GeoIP plugin performs checks during IKE_AUTH allowing richer error messaging and logging.
  • Hybrid with IdP: Firewall blocks broad regions; RADIUS/IdP rejects or issues limited sessions based on geolocation and user role. Best for enterprise SSO environments.

Checklist for deployment

  • Choose GeoIP provider and automate update cadence.
  • Select enforcement point(s): firewall, gateway, IdP, or hybrid.
  • Implement ipset-based rules or integrate with IKE daemon hooks for accurate enforcement.
  • Combine with certificate/RADIUS/MFA to mitigate spoofing and proxy usage.
  • Provide exception workflows and monitoring/alerts for blocked legitimate access.
  • Test with simulated client IPs and measure connection latencies.

Geo-based access controls are a pragmatic, high-impact layer in a defense-in-depth strategy for IKEv2 VPNs. When implemented thoughtfully—balancing strictness with operational flexibility—they reduce exposure and can significantly improve security posture without disrupting legitimate users. For more detailed guides, scripts, and policy templates tailored to strongSwan and cloud gateways, consult focused documentation and vendor best practices to fit your infrastructure.

Published on Dedicated-IP-VPN