NAT Network + port forward broken? (#18103)

[madworm]

---

ModEdit; related ticket: #18103: User-manual amendment regarding DHCP IP / NAT networking

---

NAT networking works, including DHCP. The VMs can talk to each other and see the world.
Hostonly networking works, including DHCP. The VMs can talk to each other and the host.
Private networking works, including DHCP. The VMs can only see each other.

Code: Select all

NetworkName:    natnet1
IP:             192.168.16.1
Network:        192.168.16.0/24
IPv6 Enabled:   No
IPv6 Prefix:    fd17:625c:f037:2::/64
DHCP Enabled:   Yes
Enabled:        Yes
Port-forwarding (ipv4)
        nc:tcp:[127.0.0.1]:9999:[192.168.16.137]:66
        ssh:tcp:[127.0.0.1]:6666:[192.168.16.137]:22
        telnet:tcp:[127.0.0.1]:7777:[192.168.16.137]:23
loopback mappings (ipv4)
        127.0.0.1=2

Now, the port forwarding is a different thing. I don't have any firewall active, neither on the host, nor on the VMS.

When I try to connect via ssh to one VM, I can see the connection is being made on the host (lsof -i -Pn), yet nothing really happens on the VM. The ssh daemon doesn't react in any way.
Attaching tcpdump to the relevant interface on the VM reveals that some pre connection stuff goes back and forth, a couple of SYN/ACK and ARP packets with the correct IP addresses and ports, but thats it.
Ultimately the connection fails.

What works is port forwarding with ordinary "NAT" (per VM setting), but I don't want that.

Any clues?

[madworm]

IP conflict, which didn't mess up things until I started using port-forwarding...

See https://www.virtualbox.org/ticket/18103 (request to enhance the user manual)

Don't set the DHCP server to use the IP of the gateway (AAA.BBB.CCC.1), using (AAA.BBB.CCC.3) seems to work.
This appears to be only an issue when the dhcp server is created manually, instead of using the auto-created one of "VBoxManage natnetwork add .... --dhcp on"

[socratis]

Right... What could also reveal that "mistake"/"misunderstanding" would have been the output of:

• VBoxManage list dhcpservers

See https://www.virtualbox.org/ticket/18103 (request to enhance the user manual)

Did you also post in https://www.virtualbox.org/ticket/16810 that just "woke up"?

I added the ticket information and removed the [Solved] mark since the related ticket is still open. When it gets addressed, I'll mark it as [Fixed].

[madworm]

Maybe... It's much like not seeing typos in your own writing.

[madworm]

It seems I've replicated #13753. Science

[socratis]

Great detective work, and kudos for not stopping the search!
But I think you still need to keep #18103 alive, that clarification *should* be in the manual, not in some 4-year old, closed as Invalid, ticket.