This article continues mini-series started with the post Introduction to Firewall Builder 4.0. This article is also available as a section in the "Firewall Builder Cookbook" chapter of Firewall Builder Users Guide 4.0.
Firewall Builder 4.0 is currently in beta testing phase. If you find it interesting after reading this post, please download and try it out. Source code archives, binary deb and rpm packages for popular Linux distributions and commercially distributed Windows and Mac OS X packages are available for download here.
In this post I demonstrate how Firewall Builder can be used to generate firewall configuration for a clustered web server with multiple virtual IP addresses. The firewall is running on each web server in the cluster. This example assumes the cluster is built with heartbeat using "old" style configuration files, but which high availability software is used to build the cluster is not really essential. I start with the setup that consists of two identical servers running Linux but in the end of the article I am going to demonstrate how this configuration can be converted to OpenBSD with CARP.
In this example I am working with redundant web server configuration where each machine has its own IP address, plus three additional virtual addresses that can be used for virtual hosts. Firewall Builder generates iptables script for both machines. Configuration of the HA agent should be handled either manually or using specialized configuration system such as pacemaker. When I convert the same setup from Linux to OpenBSD, I am going to show how fwbuilder can generate not only firewall configuration, but also the script that manages CARP and pfsync interfaces.
IPv6 addresses are not used in this example. Some interface objects in the screen shots have ipv6 addresses because firewall objects were "discovered" using snmp which finds ipv6 addresses. You can disregard these addresses while working with examples in this chapter.
I am going to use an "old" heartbeat configuration files in this example just to demonstrate how the configuration looks like. You should probably use modern Cluster Resource Manager software such as Pacemaker.
As shown in Figure 1, machines linux-test-1 and linux-test-2 run heartbeat daemon (Linux-HA home page) to create virtual IP addresses. Heartbeat adds virtual IP address to the same interface eth0. One of the daemons becomes master and takes ownership of the virtual address by adding it to the interface with the label "eth0:0" or "eth0:1".
Section "Linux cluster configuration with Firewall Builder" of Firewall Builder Users Guide explains that "eth0:0" is not an interface and should not be used as the name of the interface object in fwbuilder configuration.
In this example I am using heartbeat in multicast mode where it sends UDP datagram to the multicast address 126.96.36.199 every second or so to declare that it is up and running and owns the address.
If you are interested in more detailed explanation of the "old" style heartbeat configuration files used to set up example similar to this one, see Section "Linux cluster using heartbeat" of Firewall Builder Users Guide
Once heartbeat daemon is configured and started on both servers, their IP address configuration looks like shown in Figure 2 and Figure 3. Virtual addresses were highlighted to illustrate that the heartbeat is running in active/active configuration, that is, two virtual addresses are active on one machine and the third is active on another. If either machine dies, all three virtual addresses will move over to the one that is left working.
root@linux-test-1:/etc/ha.d# ip addr ls 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000 link/ether 00:0c:29:1e:dc:aa brd ff:ff:ff:ff:ff:ff inet 10.3.14.108/24 brd 10.3.14.255 scope global eth0 inet 10.3.14.150/24 brd 10.3.14.255 scope global secondary eth0:0 inet 10.3.14.151/24 brd 10.3.14.255 scope global secondary eth0:1 inet6 fe80::20c:29ff:fe1e:dcaa/64 scope link valid_lft forever preferred_lft forever
root@linux-test-2:/etc/ha.d# ip addr ls 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000 link/ether 00:0c:29:fc:67:8c brd ff:ff:ff:ff:ff:ff inet 10.3.14.109/24 brd 10.3.14.255 scope global eth0 inet 10.3.14.152/24 brd 10.3.14.255 scope global secondary eth0:0 inet6 fe80::20c:29ff:fefc:678c/64 scope link valid_lft forever preferred_lft forever
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