Virtual tunnel LAN subnet changing

b52

Hello there,

I've been just setup a OpenVPN recently, and it works really nice. I want to make a little change, switch the tunnel subnet (10.0.8.0/24) to something else. I was think of a B class subnet, limited to mask 27 (30 users).

In the server.conf, I've edited the server line to the following:

server 172.29.255.224 255.255.255.224

After that, on the client side I still receive the old subnet's IP (10.0.8.2) and it seems that routing just stopped working, since the internet is unreachable.

On the server, by checking the network adapters, the tun0 got the 172.29.255.225 address.

I think, some routing ACLs should be also updated, I just couldn't figure out where, since there arent any actibe iptable rules.

So, what is the correct way to edit the tunnel subnet?

Thanks in advance.

Pippin

A /27 will have room for 28 clients, 32-4=28.

Read here:
https://forums.openvpn.net/viewtopic.php?t=22603

b52

Pippin wrote A /27 will have room for 28 clients, 32-4=28.

Read here:
https://forums.openvpn.net/viewtopic.php?t=22603

I don't get how you got that -4, since a subnet could only preallocate netid and broadcast. GW is a host already, and which one is the fourth? Btw...thanks for the link...

Pippin

For a /24:
.0 = network
.1 = server
.254 = dhcp
.255 = broadcast

For your /27:
.244 = network
.245 = server
.254 = dhcp
.255 = broadcast

Btw... after making changes make sure to restart the server.

Jaimen

Thanks for the update and quick reply. I'll be sure to keep an eye on this thread MyGroundBiz Account

TinCanTech

Pippin wrote For your /27:
.244 = network
.245 = server
.254 = dhcp
.255 = broadcast

Correction:

ipcalc 172.29.255.224/27
Address:   172.29.255.224       10101100.00011101.11111111.111 00000
Netmask:   255.255.255.224 = 27 11111111.11111111.11111111.111 00000
Wildcard:  0.0.0.31             00000000.00000000.00000000.000 11111
=>
Network:   172.29.255.224/27    10101100.00011101.11111111.111 00000
HostMin:   172.29.255.225       10101100.00011101.11111111.111 00001
HostMax:   172.29.255.254       10101100.00011101.11111111.111 11110
Broadcast: 172.29.255.255       10101100.00011101.11111111.111 11111
Hosts/Net: 30                    Class B, Private Internet

Minus the server IP equals 29. The address you have assigned to DHCP is still a usable IP.

Pippin

The address you have assigned to DHCP is still a usable IP.

I do not assign it 😉 , the server does, check the log it's in there, iirc....
It may be usable but maybe not in all types of configuration, so I would say just don't use it.

The log of a server configured with a /24:

IFCONFIG POOL: base=10.8.0.2 size=252

That is 256-4=252

Edited.

TinCanTech

Pippin wrote The log of a server configured with a /24:

IFCONFIG POOL: base=10.8.0.2 size=252

That is 256-4=252

It is in fact the pool, starting at base .2 + 252 = .254

:mrgreen:

Pippin

You forgot the .0 .1

You're not catching me,....... this time :mrgreen:

TinCanTech

Pippin wrote You forgot the .0 .1

No, they are not included in the Pool because they are the network and server address. Also broadcast is not included in the pool.

Pippin wrote You're not catching me,....... this time :mrgreen:

Seems I just did :!: 😉

Vivian_p

The configuration of a services router running Junos OS for virtual private network (VPN) support is quite flexible. You can create route-based VPN tunnels and Network Address Translation (NAT) Official Sit can be incorporated to provide solutions for certain problematic networking scenarios. This topic discusses one such problem scenario.