Security Gateway Manual
SG-2100
11.9 Dynamic DNS
Dynamic DNS provides several benefits for multiple WANs, particularly with VPNs. If the firewall does not already
have one or more Dynamic DNS hostnames configured, consider signing up with a provider and creating one or more.
It’s a good practice to have a separate DNS entry for each WAN and a shared entry for failover, or one per failover
group. If that is not viable, at least have one for the most common needs.
The particulars of configuring Dynamic DNS entries vary by provider and are beyond the scope of this document.
11.10 VPN Considerations
IPsec can use a gateway group as an as interface, but needs a dynamic DNS hostname as companion. The remote peer
would need to use the Dynamic DNS hostname as the peer address of this firewall instead of an IP address. Because
this relies on DNS, failover can be slow.
WireGuard does not bind to an interface, but can work with Multi-WAN. It will respond from WAN2 if client contacts
WAN2, but when initiating it will always use the current default gateway. Static routes can nudge traffic for a specific
peer out a specific WAN.
OpenVPN can use a gateway group as an interface for clients or servers. Client behavior is OK and should match
default failover behavior configured on the group. For servers it is better to bind the server to localhost and use port
forwards from each WAN to localhost. Remote clients can then have multiple remote entries and contact each WAN
as needed at any time.
11.11 Testing
Methods for testing depend on the type of WANs and gateway groups in use.
• For most WANs, a better test is to unplug the
upstream
connection from the CPE. This more accurately simu-
lates a typical type of upstream connectivity failure. Do not power off the CPE or unplug the connection between
the firewall and the CPE. While this may work, it’s a much less common scenario and can behave differently.
• For testing load balancing, use cURL or multiple browsers/sessions when checking the IP address multiple
times. Refreshing the same browser window will reuse a connection to the server and is not helpful for testing
connection-based load balancing.
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