IPSec VPN with Dynamic Peers on Palo Alto Firewalls

Overview

Establishing IPSec VPN connections with dynamic peers on Palo Alto Networks firewalls requires specific configurations to accommodate changing IP addresses. Utilizing identifiers like FQDN or User FQDN ensures reliable authentication and connectivity.

1. Configure IKE Gateway on Dynamic Peer

• Interface: Select the external interface receiving the dynamic IP.
• Local Identification: Set to a unique identifier, such as a User FQDN (e.g., branch1@example.com ).
• Peer IP Address Type: Set to Dynamic .
• Authentication: Choose Pre-shared Key and enter a secure key.
• Enable Passive Mode: Do not enable. The dynamic peer must initiate the connection.

Note: The dynamic peer must initiate the VPN connection since its IP address is not known to the static peer.

7. Configuring Certificate-Based Authentication for Dynamic Peers

Utilizing digital certificates for IPSec VPN authentication enhances security by eliminating the need for pre-shared keys. This method is particularly beneficial when dealing with dynamic peers, as it allows for flexible and secure identification without relying on static IP addresses.

Steps to Implement Certificate-Based Authentication:

1. Generate or Import Certificates:
   • Navigate to Device > Certificate Management > Certificates on the Palo Alto firewall.
   • Import an existing certificate or generate a new one. Ensure that the certificate includes the appropriate Subject Alternative Name (SAN) entries, such as FQDNs, to identify the peer.
   • If importing, select the correct file format (e.g., PEM or PKCS12) and provide the necessary passphrase if required.
   • For detailed instructions, refer to Palo Alto Networks' documentation on Importing a Certificate for IKEv2 Gateway Authentication .
2. Configure the IKE Gateway:
   • Go to Network > Network Profiles > IKE Gateways and add a new gateway.
   • Under the General tab, set the Authentication method to Certificate .
   • Select the appropriate Local Certificate from the dropdown menu.
   • If the peer's IP address is dynamic, set the Peer IP Address Type to Dynamic .
   • Ensure that the Peer Identification matches the identifier specified in the peer's certificate (e.g., FQDN).
3. Exporting Certificates Using Hash and URL (Optional):
   • For IKEv2, Palo Alto Networks supports the Hash and URL method for certificate exchange.
   • This approach allows the peer to fetch the certificate from a specified HTTP server, reducing the size of IKE messages and minimizing fragmentation.
   • To enable this, select HTTP Certificate Exchange in the IKE Gateway configuration and provide the URL where the certificate is hosted.
   • For more information, see Palo Alto Networks' guide on Exporting a Certificate for a Peer to Access Using Hash and URL .
4. Finalize IPSec Tunnel Configuration:
   • Proceed to configure the IPSec Tunnel by associating it with the IKE Gateway configured for certificate-based authentication.
   • Ensure that the IPSec Crypto Profile matches on both peers and that the tunnel interface is correctly assigned to the appropriate virtual router and security zone.

Considerations:

• Ensure that both peers trust the Certificate Authority (CA) that issued the certificates.
• Regularly monitor certificate expiration dates and renew certificates as needed to maintain uninterrupted VPN connectivity.
• When dealing with dynamic peers, it's crucial that the peer initiates the VPN connection, as the static peer cannot predict the dynamic peer's IP address.

Implementing certificate-based authentication provides a robust and scalable solution for securing IPSec VPNs, especially in environments with dynamic IP addressing.

2. Configure IKE Gateway on Static Peer

• Peer IP Address Type: Set to Dynamic .
• Peer Identification: Enter the same identifier used as the Local Identification on the dynamic peer (e.g., branch1@example.com ).
• Authentication: Use the same pre-shared key configured on the dynamic peer.
• Enable Passive Mode: Enable this option to allow the static peer to respond to incoming connections.

Note: The static peer cannot initiate the connection since it does not have the dynamic peer's IP address.

3. Configure IPSec Tunnel

• Tunnel Interface: Assign a tunnel interface (e.g., tunnel.1 ).
• IKE Gateway: Select the IKE Gateway configured in the previous steps.
• IPSec Crypto Profile: Choose a profile that matches the encryption and authentication settings on both peers.

4. Configure Security Policies and Routing

• Create security policies to allow traffic between the internal network and the VPN tunnel.
• Configure routing to direct traffic destined for the remote network through the tunnel interface.

5. Considerations for Both Peers with Dynamic IPs

Establishing a VPN between two peers with dynamic IP addresses is not supported on Palo Alto Networks firewalls. At least one peer must have a static IP address to initiate the connection reliably.

Reference: IPSEC VPN support for both side as Dynamic

6. Additional Resources

• IPSec VPN Tunnel with Peer Having Dynamic IP Address
• Configuring IPSec VPN between Palo Alto Firewall & Meraki MX