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Can't connect to host after enabling WireGuard tunnel

I installed WireGuard on my host and set this configuration /etc/wireguard/wg0.conf:


<span style="color:#323232;">[Interface]
</span><span style="color:#323232;">Address = 10.0.0.1/24
</span><span style="color:#323232;">ListenPort = 51820
</span><span style="color:#323232;">PrivateKey = [REDACTED]
</span><span style="color:#323232;">PostUp = iptables -A FORWARD -i %i -j ACCEPT; iptables -t nat -A POSTROUTING -o ens3 -j MASQUERADE
</span><span style="color:#323232;">PostDown = iptables -D FORWARD -i %i -j ACCEPT; iptables -t nat -D POSTROUTING -o ens3 -j MASQUERADE
</span><span style="color:#323232;">
</span><span style="color:#323232;">
</span><span style="color:#323232;">[Peer]
</span><span style="color:#323232;">PublicKey = [REDACTED]
</span><span style="color:#323232;">PresharedKey = [REDACTED]
</span><span style="color:#323232;">AllowedIPs = 10.0.0.2/32
</span><span style="color:#323232;">
</span><span style="color:#323232;">[Peer]
</span><span style="color:#323232;">PublicKey = [REDACTED]
</span><span style="color:#323232;">PresharedKey = [REDACTED]
</span><span style="color:#323232;">AllowedIPs = 10.0.0.3/32
</span><span style="color:#323232;">
</span><span style="color:#323232;">[Peer]
</span><span style="color:#323232;">PublicKey = [REDACTED]
</span><span style="color:#323232;">PresharedKey = [REDACTED]
</span><span style="color:#323232;">AllowedIPs = 10.0.0.4/32
</span><span style="color:#323232;">
</span><span style="color:#323232;">[Peer]
</span><span style="color:#323232;">PublicKey = [REDACTED]
</span><span style="color:#323232;">PresharedKey = [REDACTED]
</span><span style="color:#323232;">AllowedIPs = 10.0.0.5/32
</span><span style="color:#323232;">
</span><span style="color:#323232;">[Peer]
</span><span style="color:#323232;">PublicKey = [REDACTED]
</span><span style="color:#323232;">PresharedKey = [REDACTED]
</span><span style="color:#323232;">AllowedIPs = 10.0.0.6/32
</span><span style="color:#323232;">
</span><span style="color:#323232;">[Peer]
</span><span style="color:#323232;">PublicKey = [REDACTED]
</span><span style="color:#323232;">PresharedKey = [REDACTED]
</span><span style="color:#323232;">AllowedIPs = 10.0.0.7/32
</span><span style="color:#323232;">
</span><span style="color:#323232;">[Peer]
</span><span style="color:#323232;">PublicKey = [REDACTED]
</span><span style="color:#323232;">PresharedKey = [REDACTED]
</span><span style="color:#323232;">AllowedIPs = 10.0.0.8/32
</span><span style="color:#323232;">
</span><span style="color:#323232;">[Peer]
</span><span style="color:#323232;">PublicKey = [REDACTED]
</span><span style="color:#323232;">PresharedKey = [REDACTED]
</span><span style="color:#323232;">AllowedIPs = 10.0.0.9/32
</span><span style="color:#323232;">
</span><span style="color:#323232;">[Peer]
</span><span style="color:#323232;">PublicKey = [REDACTED]
</span><span style="color:#323232;">PresharedKey = [REDACTED]
</span><span style="color:#323232;">AllowedIPs = 10.0.0.10/32
</span><span style="color:#323232;">
</span><span style="color:#323232;">[Peer]
</span><span style="color:#323232;">PublicKey = [REDACTED]
</span><span style="color:#323232;">PresharedKey = [REDACTED]
</span><span style="color:#323232;">AllowedIPs = 10.0.0.11/32
</span><span style="color:#323232;">
</span>

Nmap scan when wg0 is down:


<span style="color:#323232;">Starting Nmap 7.93 ( https://nmap.org ) at 2024-08-16 03:26 CDT
</span><span style="color:#323232;">Host is up (0.050s latency).
</span><span style="color:#323232;">Not shown: 998 closed tcp ports (conn-refused)
</span><span style="color:#323232;">PORT    STATE    SERVICE
</span><span style="color:#323232;">22/tcp  open     ssh
</span><span style="color:#323232;">179/tcp filtered bgp
</span><span style="color:#323232;">
</span><span style="color:#323232;">Nmap done: 1 IP address (1 host up) scanned in 1.93 seconds
</span>

Nmap scan when wg0 is up:


<span style="color:#323232;">Starting Nmap 7.93 ( https://nmap.org ) at 2024-08-16 03:27 CDT
</span><span style="color:#323232;">All 1000 scanned ports are in ignored states.
</span><span style="color:#323232;">Not shown: 1000 filtered tcp ports (no-response)
</span><span style="color:#323232;">
</span><span style="color:#323232;">Nmap done: 1 IP address (1 host up) scanned in 201.43 seconds
</span><span style="color:#323232;">
</span>

I also cannot connect to host via ssh. How to fix this issue?

atzanteol ,

What does your client config look like? What IP are you connecting to for nmap/ssh?

user_naa OP ,

I didn’t connect any client yet.

Muehe ,

I think the problem might be your PostUp/PostDown lines have an in-interface (-i) but are missing an out-interface (-o) for the forwarding. Try this:


<span style="color:#323232;">PostUp   = iptables -A FORWARD -i %i -j ACCEPT; iptables -A FORWARD -o %i -j ACCEPT; iptables -t nat -A POSTROUTING -o ens3 -j MASQUERADE
</span><span style="color:#323232;">PostDown = iptables -D FORWARD -i %i -j ACCEPT; iptables -D FORWARD -o %i -j ACCEPT; iptables -t nat -D POSTROUTING -o ens3 -j MASQUERADE
</span>
just_another_person ,

Because the default route is changing. You have ALL traffic being routed over Wireguard here. How would you expect that to allow the interface routing to work for the local network if you’re telling this to punt all traffic to this specific connection?

user_naa OP ,

What is correct config?

user_naa OP ,

I removed all PostUp rules and cleared iptables but still the same problem

just_another_person ,

Well, I mean…I can’t give you an entire tutorial on how Wireguard works here, but you have it way wrong.

If you’re not sure of the concepts and what you’re trying to do, I don’t know how to answer any questions for you. If you’re not familiar with what split-tunneling, subnet routing, and routing tables…you need to get way familiar before you start messing with this.

Your rules aren’t the problem. You’re only allowing a single IP at a time across many connections here. Learn to read your routing tables and debug from there.

Muehe ,

You have ALL traffic being routed over Wireguard here.

Please correct me if I’m wrong, but isn’t it the other way around? All Wireguard traffic is forwarded to the local interface.

just_another_person ,

AllowdIPs defines the traffic to be routed. These are single IPs, not subnets.

Edit: discussion talking about this same problem to illustrate: forum.gl-inet.com/t/…/31318

Muehe ,

I don’t think that’s what the setting does. Anyway, I have them set to a /32 IP in my server config and it works nonetheless. I get full access to the /24 behind the server from the client.

just_another_person ,

That’s exactly what it does. Easy to see if OP new how to read their route tables.

Here’s another: serverfault.com/…/wireguard-policy-based-routing

Muehe ,

What are you trying to say? That reply also shows AllowedIPs set to a /32 on the server side.

just_another_person ,

For Peers. There’s no other route in OPs post. Like they said, when wg0 goes up, he can’t reach anything else. All that happens is this interface comes out, changes the routing tables and forwarding, but doesn’t go anywhere. It needs to be routed to the existing default gateway of the host. All this does is blackhole to the wg0 interface.

Muehe ,

Like I said in another thread on this post, I’m pretty sure that’s because they are forwarding input but not output in the PostUp rules. Setting a /32 in AllowedIPs works fine for me.

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