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docs/Networking/Sophos/IPSec Site-to-Site VPN Tunnel.md

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Purpose: You may have two Sophos XGS appliances (or a mixed configuration) and need to set up a site-to-site VPN tunnel between two remote locations. You can achieve this with a simple passphrase-based IPSec VPN tunnel.

!!! info "Assumptions" This documentation only provides instruction for Sophos XGS based devices. It does not account for third-party vendors or other manufactured hardware. If you need to set up a mixed VPN tunnel with a different brand of networking device, you need to do your best to match the settings on the tunnels manually. (e.g. Encryption Type, Phase Lifetimes, etc).

Login to the Firewall

You will need to access the firewall either directly on the local network at https://<IP-of-Firewall>:4444 or remotely in Sophos Central.

Configure an IPSec VPN Tunnel

Navigate to "Configure > Site-to-Site VPN > Add"

General settings

Field Value
Name <ThisLocation> to <RemoteLocation>
IP Version Dual
Connection Type Tunnel Interface (Also known as a "Route-Based VPN")
Gateway Type Initiate the Connection / Respond Only (See "Best Practices" Section)

Encryption

Field Value
Encryption Profile Custom_IKEv2_Initiator / Custom_IKEv2_Responder (Based on the "Gateway Type")
Authentication Type Preshared Key / Passphrase

Gateway Settings

Field Value
Listening Interface <WAN Interface / Generally "Port2"> (Internal IP Address)
Gateway Address <Public IP of Remote Firewall>
Local ID Type IP Address (Usually Optional)
Remote ID Type <If the Remote Firewall has one, enter it, otherwise leave blank> (Usually Optional)
Local Subnet <Leave Blank>
Remote Subnet <Leave Blank>

!!! tip "Best Practices - Initiators / Responders" If you have a hub-and-spoke network, where one location acts as a central authority (e.g. domain controllers, auth servers, identity providers, headquarters, etc), you will set up the central "hub" as a VPN responder on its side of the VPN tunnel, and all the remote "spoke" locations would behave as VPN initiators.

!!! note "Tunnel IDs / Subnets" If one side of the tunnel indicates a Local ID, you need to input that as the Remote ID on the other end of the tunnel. While Tunnel IDs are generally optional, if one side uses them, both need to.

- "Route-Based" VPNs do not need subnets indicated / configured
- "Policy-based" VPNs require subnets indicated / configured

Configure IPSec Encryption Profile

Navigate to "System > Profiles > IPSec Profiles > Custom_IKEv2_<Initiator>/<Responder>"

Field Value
Phase 1 Lifetime <Longer Lifetime Compared to Phase 2> (If Initiator)
Phase 2 Lifetime <Shorter Lifetime Compared to Phase 1> (If Initiator)

!!! warning "Remote / Local Phase Lifetimes" Within the context of the remote and local VPN tunnels, the lifetime of the Phase 1 and Phase 2 encryption keys needs to be shorter on the intiator than the responder sides of the VPN tunnel.

Connect the IPSec tunnels

Now you need to start the tunnel on the Initiator side first, then start the tunnel on the responder side. If both sides show green status indicators, the tunnel should be active.