# OpenVPN 2.3.8 topology subnet not normal!



## hzdtony (Nov 5, 2015)

I am via port installed OpenVPN 2.3.8 on the FreeBSD 8.4 and 10.2.But start openvpn use --topology subnet option,tun0 interface  allocate two ip address 1-->2.I have Post this problem to openvpn forums and send email to mandree@freebsd.org,but problem still not solve!
openvpn forums(link:https://forums.openvpn.net/topic19809.html) have problem detail describe!Hope this is problem can solve.Thanks everyone!


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## SirDice (Nov 5, 2015)

It's not a bug, it's a misconception. The output of ifconfig(1) shows two IP addresses, this is normal and correct. It shows both the local and remote IP addresses of the tunnel. The Linux ifconfig simply presents it differently.


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## hzdtony (Nov 5, 2015)

I have a now running FreeBSD 8.4,installed openvpn 2.3.6,tun0 interface is shows one IP address.

```
root@gwvpn:~# openvpn --version  20151105 15:45:34
OpenVPN 2.3.6 amd64-portbld-freebsd8.4 [SSL (OpenSSL)] [LZO] [MH] [IPv6] built on Dec  3 2014
library versions: OpenSSL 1.0.1j 15 Oct 2014, LZO 2.06
Originally developed by James Yonan
Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
Compile time defines: enable_crypto=yes enable_crypto_ofb_cfb=yes enable_debug=yes enable_def_auth=yes enable_dlopen=unknown enable_dlopen_self=unknown enable_dlopen_self_static=unknown enable_fast_install=needless enable_fragment=yes enable_http_proxy=yes enable_iproute2=no enable_libtool_lock=yes enable_lzo=yes enable_lzo_stub=no enable_management=yes enable_multi=yes enable_multihome=yes enable_pam_dlopen=no enable_password_save=no enable_pedantic=no enable_pf=yes enable_pkcs11=no enable_plugin_auth_pam=yes enable_plugin_down_root=yes enable_plugins=yes enable_port_share=yes enable_selinux=no enable_server=yes enable_shared=yes enable_shared_with_static_runtimes=no enable_small=no enable_socks=yes enable_ssl=yes enable_static=yes enable_strict=no enable_strict_options=no enable_systemd=no enable_win32_dll=yes enable_x509_alt_username=no with_crypto_library=openssl with_gnu_ld=yes with_mem_check=no with_plugindir='$(libdir)/openvpn/plugins' with_sysroot=no
root@gwvpn:~# ifconfig tun0  20151105 15:45:46
tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1500
   options=80000<LINKSTATE>
   inet 10.0.27.1 --> 10.0.27.1 netmask 0xffffff00
   Opened by PID 867
root@gwvpn:~# uname -a  20151105 15:45:53
FreeBSD gwvpn 8.4-RELEASE-p35 FreeBSD 8.4-RELEASE-p35 #0: Tue Jul 28 10:55:26 UTC 2015  root@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  amd64
```


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## SirDice (Nov 5, 2015)

I'm really struggling to understand what you mean. Please explain it in as much detail as possible.


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## kpa (Nov 5, 2015)

When you use a tun(4) device there has to be two addresses because the device forces point-to-point semantics. However with the "subnet" topology the client is given only one address and that's the reason for what you're seeing.


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## hzdtony (Nov 6, 2015)

Thank a lot! I upload three screenshots. Separately is OpenVPN subnet explian and OpenVPN 2.3.8 on the Linux and FreeBSD compare case. Last one is I now running on the FreeBSD 8.4 and OpenVPN 2.3.6 Server, and tun0 interface have a IP address on the FreeBSD 8.4 and 10.2 tun interface realization principle not same? or OpenVPN 2.3.6  between 2.3.8 occur changed?


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