Technical Tip: IPsec VPN between static and dynamic IP (FQDN)
Description
This article describes how to create a site-to-site VPN between FortiGates where the remote site has a dynamic IP address and local FortiGate has a static IP address.
Scope
FortiGate.
Solution
On the local FortiGate, the dynamic IP address of the remote site is used as the remote-gateway (in this case, a remote firewall FQDN address).
Note: The remote gateway can only be modified to DDNS via CLI once IPsec Phase1 is created.
edit "frtest"
set type ddns
set interface "wan1"
set peertype any
set net-device disable
set proposal aes128-sha256 aes256-sha256 aes128-sha1 aes256-sha1
set wizard-type static-fortigate
set remotegw-ddns "testbran.fortiddns.com"
next
edit "frtest"
set phase1name "frtest"
set proposal aes128-sha1 aes256-sha1 aes128-sha256 aes256-sha256 aes128gcm aes256gcm chacha20poly1305
set src-addr-type name
set dst-addr-type name
set src-name "frtest_local"
set dst-name "frtest_remote"
next
end
Note.
The remote-end firewall has a dynamic IP address instead of a static IP address, so an FQDN (fully qualified domain name) is configured as the gateway configuration.
For the IPSEC configuration on remote FortiGate in GUI.
Go to VPN -> IPsec Wizard .
- Set the Name <ere>
- Select the Template type Site-to-Site
- Set the Remote IP address <static IP address>
- Select the local interface and subnets.
After the above setup, similar settings as shown below are visible (the Remote Gateway is Static IP address which is 10.5.22.98 in this example).
vd: root/0
name: frtest
version: 1
interface: wan1 7
addr: 10.5.22.98:4500 -> 10.5.21.219:64916 <----- Resolved FQDN IP is listed.
created: 3199s ago
nat: peer
IKE SA: created 1/2 established 1/1 time 20/20/20 ms
IPsec SA: created 1/2 established 1/1 time 20/20/20 ms
id/spi: 23274 fdc5a41724a8e065/ed8c3e19adb75840
direction: responder
status: established 3194-3194s ago = 20ms
proposal: aes128-sha256
key: 3c359876a94b04d2-b70eade19fc29822
lifetime/rekey: 86400/82935
DPD sent/recv: 00000000/00000000
Note:
When a FortiGate that connects to remote gateway using DDNS loses connectivity to the DNS servers, the VPN tunnel will fail to connect.
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