169 lines
4.1 KiB
Plaintext
169 lines
4.1 KiB
Plaintext
---
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title: "WireGuard VPN with 2 or more subnets"
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description: "How to connect 2 subnets with WireGuard."
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date: 2019-02-14T21:38:28+01:00
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draft: false
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tags:
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- wireguard
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- vpn
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comtodon: 9fqBQKGZa6qMf98wIC
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---
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:source-highlighter: pygments
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I wanted to create a https://en.wikipedia.org/wiki/WireGuard[WireGuard] VPN with
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2 subnets in different physical places, each with their own server. I couldn't
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find an example how to do that, so I wrote this one.
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== Introduction
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This HowTo is Linux specific.
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I'm going to use the IP range `fd69::/48` for the VPN, `fd69:0:0:1::/64` for
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subnet 1 and `fd69:0:0:2::/64` for subnet 2. I'm going to call the server of
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subnet 1 `server1`, its first client `client1a`, the second one `client1b` and
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so on.
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All clients in subnet 1 will connect to `server1` and all clients in subnet 2
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will connect to `server2`. `server1` and `server2` will be connected. If
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`client1a` wants to connect to `client2a`, the route will be:
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`client1a → server1 → server2 → client2a`.
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== Preparations
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https://www.wireguard.com/install/[Install WireGuard], create `/etc/wireguard`
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and generate a key-pair on each participating peer.
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[source,shell]
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----
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mkdir /etc/wireguard
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cd /etc/wireguard
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umask 077
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wg genkey | tee privatekey | wg pubkey > publickey
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----
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== Configure servers
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.Turn on IP forwarding:
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[source,shell]
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----
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echo "net.ipv6.conf.all.forwarding = 1" > /etc/sysctl.d/ip-forward.conf
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sysctl -p /etc/sysctl.d/ip-forward.conf
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----
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[NOTE]
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http://strugglers.net/~andy/blog/2011/09/04/linux-ipv6-router-advertisements-and-forwarding/[IP forwarding will put your computer into "router-mode"],
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it will no longer autoconfigure via https://en.wikipedia.org/wiki/SLAAC[SLAAC].
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If you need SLAAC, add `net.ipv6.conf.DEVICE.accept_ra = 2` to `ip-forward.conf`.
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.`server1:/etc/wireguard/wg0.conf`:
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[source,cfg]
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----
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# This peer
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[Interface]
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Address = fd69:0:0:1::1/48
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PrivateKey = <PRIVATE KEY OF server1>
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ListenPort = 51820
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# Server of subnet 2
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[Peer]
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PublicKey = <PUBLIC KEY OF server2>
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Endpoint = server2:51820
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AllowedIPs = fd69:0:0:2::/64
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# Clients of subnet 1
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[Peer]
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PublicKey = <PUBLIC KEY OF client1a>
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AllowedIPs = fd69:0:0:1::a/128
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[Peer]
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PublicKey = <PUBLIC KEY OF client1b>
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AllowedIPs = fd69:0:0:1::b/128
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----
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.`server2:/etc/wireguard/wg0.conf`:
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[source,cfg]
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----
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# This peer
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[Interface]
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Address = fd69:0:0:2::1/48
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PrivateKey = <PRIVATE KEY OF server2>
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ListenPort = 51820
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# Server of subnet 1
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[Peer]
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PublicKey = <PUBLIC KEY OF server1>
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Endpoint = server1:51820
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AllowedIPs = fd69:0:0:1::/64
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# Clients of subnet 2
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[Peer]
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PublicKey = <PUBLIC KEY OF client2a>
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AllowedIPs = fd69:0:0:2::a/128
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----
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== Configure clients
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.`client1a:/etc/wireguard/wg0.conf`:
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[source,cfg]
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----
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[Interface]
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Address = fd69:0:0:1::a/48
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PrivateKey = <PRIVATE KEY OF client1a>
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[Peer]
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PublicKey = <PUBLIC KEY OF server1>
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Endpoint = server1:51820
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AllowedIPs = fd69::/48
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PersistentKeepalive = 25
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----
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.`client1b:/etc/wireguard/wg0.conf`:
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[source,cfg]
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----
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[Interface]
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Address = fd69:0:0:1::b/48
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PrivateKey = <PRIVATE KEY OF client1b>
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[Peer]
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PublicKey = <PUBLIC KEY OF server1>
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Endpoint = server1:51820
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AllowedIPs = fd69::/48
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PersistentKeepalive = 25
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----
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.`client2a:/etc/wireguard/wg0.conf`:
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[source,cfg]
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----
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[Interface]
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Address = fd69:0:0:2::a/48
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PrivateKey = <PRIVATE KEY OF client2a>
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[Peer]
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PublicKey = <PUBLIC KEY OF server2>
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Endpoint = server1:51820
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AllowedIPs = fd69::/48
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PersistentKeepalive = 25
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----
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The `AllowedIPs` setting acts as a routing table. When a peer tries to send a
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packet to an IP, it will check `AllowedIPs`, and if the IP appears in the list,
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it will send it through the WireGuard interface.
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The `PersistentKeepalive` setting ensures that the connection is maintained and
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that the peer continues to be reachable, even behind a NAT.
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== Start VPN
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Run `wg-quick up wg0` on each peer.
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== Further reading
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The article https://www.stavros.io/posts/how-to-configure-wireguard/[How to easily configure WireGuard]
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by Stavros Korokithakis helped me a great deal in understanding WireGuard.
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== Updates
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* Updated 2019-02-16 to include IP forwarding.
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* Updated 2019-02-16 with information on how to turn SLAAC back on.
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