Basic stupid newbie question about gateway address

ovpnalexs

Hello, I have a stupid newbie question, just want some background...

Everything seems to be working with OpenVPN/Alpine, but I just want to understand something....

On my openVPN server (on Alpine server via docker container), route -n produces:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.0.1     0.0.0.0         UG    0      0        0 eth0
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
192.168.254.0   192.168.255.2   255.255.255.0   UG    0      0        0 tun0
192.168.255.0   192.168.255.2   255.255.255.0   UG    0      0        0 tun0
192.168.255.2   0.0.0.0         255.255.255.255 UH    0      0        0 tun0

When client connects with OpenVPN the gateway ends up on 192.168.255.5 when my LAN gateway is actually 192.168.0.1

This is normal I assume (it works) but if somebody could please explain in fairly simplistic terms why gateway has changed. I'm assuming the subnets would not be able to ping each otherwise, and I assume some mapping is going on... just need a better explanation of how it works/what is going on...

Thanks!

TinCanTech

ovpnalexs wrote why gateway has changed

Your gateway has not changed, your routing has.

ovpnalexs

Right.... So I just want to know why it sets up another gateway address.

That gateway is just set up to route the the other gateway by openVPN?

TinCanTech

That is how networks work.

I suggest you buy a book on the subject .. https://openvpn.net/community-resources/#books

ovpnalexs

Oh really?

I didn't manually set this up, I assume OpenVPN does this, so this kinda gets out of my comfort zone and I want to know the specifics of what is actually going on.

If I set up the routing table myself it would have been clearer.

Anyway I already admitted in the title this was a stupid newbie question and was hoping for responses that are a little less patronising. Seems like this isn't a particularly friendly space to have a discussion (this from a moderator),.so sorry for wasting your time - bye.

TinCanTech

Every route has a gateway and there is also your default-gateway.

ovpnalexs

Yes I know.
Just forget it

TinCanTech

If you suddenly know now, why bother asking in the first place .. ?

Start here: https://community.openvpn.net/openvpn/wiki/HOWTO

ovpnalexs

Perhaps read again what I wrote earlier again, I was looking at what OpenVPN was doing/setting up automatically with gateways.I wasn't asking for a network topology lesson.

Anyway at risk of repeating myself,.you've being pretty rude so please just forget it, you're just going to write unhelpful and belittling one liners rather than engage in any meaningful discussion. So please stop wasting your time communicating with me.

TinCanTech

Perhaps, you now understand the nature of a gateway and why yours was not changed, perhaps not..

ovpnalexs

Perhaps see previous response.

openvpn_inc

ovpnalexs wrote Right.... So I just want to know why it sets up another gateway address.

That gateway is just set up to route the the other gateway by openVPN?

Hi,

The tun0 interface is really just a point-to-point connection, but the topology subnet feature makes it act like a real subnet. That is why you need a gateway to reach your server subnet. You have the direct link to the server, and the server address is your gateway to the VPN network[s].

BTW you could have combined 192.168.254.0/24 and 192.168.255.0/24 into a single 192.168.254.0/23.

regards, rob0

ovpnalexs

openvpn_inc wrote
ovpnalexs wrote Right.... So I just want to know why it sets up another gateway address.

That gateway is just set up to route the the other gateway by openVPN?
Hi,

The tun0 interface is really just a point-to-point connection, but the topology subnet feature makes it act like a real subnet. That is why you need a gateway to reach your server subnet. You have the direct link to the server, and the server address is your gateway to the VPN network[s].

BTW you could have combined 192.168.254.0/24 and 192.168.255.0/24 into a single 192.168.254.0/23.

regards, rob0

Perfect thankyou!