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It's time to replace old server with new one. In old server all was setup on bare metal. With new server I try to set up virtual server for specific task.

Host OS is Debian 9. Guests I will run in HVM mode (also Debian). Planned servers are: MySql, email (postfix,curys,spam filters and all related to email), web server (nginx+php), web proxy (SSL terminator)

But question is about networking. I do not want that guests are visible from outside and they do not have public IP. But each guest must see other guests.

I created two bridges. hostbr0 and xenbr0. In hostbr0 I added physical interface eno1 witch has one static IP (public). In xenbr0 I added vdum1 interface.

vdum1 is virtual interface with dummy module, IP = 192.168.1.1. For all guests IP address is from 192.168.1.0 subnet. So all guests are in one network.

How I can configure iptables, so that guests have internet access? I am not asking for exact commands but for directions. Do I need to setup masquerading? Then witch interface must masquerade? Is it possible to set forwarding between bridges?

I already tried masquerading booth bridges and also interfaces but I cannot access internet from guest OS.

I also want to control guest access to internet. For example, mysql guest do not need internet at all (in general).

On host OS I will use shorewall.

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On host OS, you add a rule on IPTables which performs SNAT to the packets coming in from the internal guest and going outside.

In Shorewall, the entry looks like this in /etc/shorewall/masq:

eth0    192.168.10.1    10.10.10.10

Here, eth0 is the interface connecting to the internet. 192.168.10.1 is the guest IP address you want to NAT. 10.10.10.10 is the IP address the packets will receive after SNAT (usually this is the same as host OS public IP address).

  • I will try it in this week and then report results. – Guntis Oct 2 '17 at 19:19

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