Openvpn nat and iptables


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Openvpn nat and iptables

good day good people

hi

first to tell that firewall and vpn is working as expected, but I notice something strange.

I have host system 11.11.11.11(local ip) firewall is blocking everything except port to vpn.
I have vpn on virtualized system 22.22.22.22 (CentOS both host and virtual). They are behind MikroTik router and then to my ISP router. This is a home setup I'm just experimenting.

PREROUTING 11.11.11.11:1194 to 22.22.22.22:1194 all other is blocked by iptables.
POSTROUTING 22.22.22.22 to 11.11.11.11

I noticed with Wireshark from host 11.11.11.11 that while I'm connected to vpn from another pc that 11.11.11.11 is connecting to ip addresses of websites I visit while in same time is connected to vpn. like:

11.11.11.11 XX.XX.XX public ip
11.11.11.11 tcp udp sites i visit

but 11.11.11.11 is unnecessarily making connections to website ip addresses. She cannot make the reqests because DNS and ports for that are blocked. So this is because postrouting command my best guess. Can this somehow be disabled? First this is a security issue, second its unnecessary.

Someone told me that this is because NAT setup. but I believe that this can be disabled somehow, I didn't find solution yet so maybe someone know how.

thanks


Moderator's Comments:
Mod Comment We had to correct a lot of spelling errors. Please put more effort into using proper english

Last edited by Scrutinizer; 11-05-2016 at 04:48 AM.. Reason: Spelling
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IPTABLES-SAVE(8)                                                  iptables 1.6.1                                                  IPTABLES-SAVE(8)

NAME
iptables-save -- dump iptables rules to stdout ip6tables-save -- dump iptables rules to stdout SYNOPSIS
iptables-save [-M modprobe] [-c] [-t table] ip6tables-save [-M modprobe] [-c] [-t table] DESCRIPTION
iptables-save and ip6tables-save are used to dump the contents of IP or IPv6 Table in easily parseable format to STDOUT. Use I/O-redirect- ion provided by your shell to write to a file. -M, --modprobe modprobe_program Specify the path to the modprobe program. By default, iptables-save will inspect /proc/sys/kernel/modprobe to determine the exe- cutable's path. -c, --counters include the current values of all packet and byte counters in the output -t, --table tablename restrict output to only one table. If not specified, output includes all available tables. BUGS
None known as of iptables-1.2.1 release AUTHORS
Harald Welte <laforge@gnumonks.org> Rusty Russell <rusty@rustcorp.com.au> Andras Kis-Szabo <kisza@sch.bme.hu> contributed ip6tables-save. SEE ALSO
iptables-apply(8),iptables-restore(8), iptables(8) The iptables-HOWTO, which details more iptables usage, the NAT-HOWTO, which details NAT, and the netfilter-hacking-HOWTO which details the internals. iptables 1.6.1 IPTABLES-SAVE(8)

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