izBalancing

izBalancing allow your linux firewall to become a multihomed input/output loadbalanced internet gateway with failover facility
Author: Ugo Viti ugo.viti@initzero.it

What is this?

This bash script allow you to easly and fastly configure a complex Load Balancing Multi Homed Internet Gateway for inbound and outbound traffic

Key Features:

Multiple balanced default gateway configuration
Load Balanced outgoing connections from LAN to INTERNET connections
Management of multiple incoming connection from many INTERNET ISP lines to DMZ/LAN Servers
SystemV compliant script... you can run easly at boot up (like Red Hat, Fedora, SuSE, Mandrake, etc...)
Automatically discover your local IP addresses... you can change your IP without reconfigure this script, just restart
Start and Stop cleanly your multihomed configuration with simple command (izbalancing start|stop|restart)
Adding new internet connections is very fast and easy
You must provide the interface name, router ip address and a descriptive name only
If the izping daemon is installed into /etc/rc.d/init.d/ it will be used for automatic failover and recovery of internet lines

Requirements:

GNU/Linux Firewall running Kernel >=2.6.10 (with iptables module CONNMARK available)
Bash Shell >= 2.0
Standard GNU/Linux coreutils utilities (cat, echo, grep, if, etc...)
GNU Version of awk and sed utilities
GNU/Linux Netfilter user space utilities (iptables >= 1.2.11)
iproute2 utilities
Two or more Internet connections (also from different ISPs and IP classes)
An ethernet card for each ISP Router

Tested On:

GNU/Linux CentOS 6 with 3 internet connections

Network Topology Example:

+----------+                       +-------------------+  192.168.254.254+----------+             +-------+                
| Server x +<--+                   | 192.168.254.1:eth1+<--------------->+ Router 1 +<----------->+ ISP 1 +<--+            
+----------+   |                   |                   |                 +----------+ ADSL line 1 +-------+   |            
               |                   |    GNU/Linux      |                                                      |            
+----------+   |   192.168.1.1:eth0|                   |  192.168.253.254+----------+             +-------+   |            
| Server y +<--+---+LAN+---------->+ 192.168.253.1:eth2+<--------------->+ Router 2 +<----------->+ ISP 2 +<--+---->INTERNET
+----------+   |                   |                   |                 +----------+ HDSL line 2 +-------+   |            
               |                   |     Firewall      |                                                      |            
+----------+   |                   |                   |  192.168.nnn.nnn+----------+             +-------+   |            
| Server z +<--+                   | 192.168.nnn.n:ethn+<--------------->+ Router n +<----------->+ ISP n +<--+            
+----------+                       +-------------------+                 +----------+  T3 line n  +-------+

Installation:

If using a Red Hat Linux based distribution, just copy the izbalancing script into /etc/init.d/ and run:

  chmod 755 /etc/init.d/izbalancing
  chkconfig izbalancing on

Configure or add the following variables into this script:

  GATEWAYS="interface1:gatewayip1:name1 interface2:gatewayip2:name2 interface3:gatewayip3:name3"
  BALANCED="name1 name2"
  VERIFY_HOSTS="ip1 ip2 ip3"
  FAILOVER_HOSTS="ip4 ip5 ip6"

Comment out the iptables rules as you need
usable special variables created on demand using the order specified in the GATEWAYS variable:

  $GWIFx = interface name (ex. GWIF1=eth1, GWIF2=eth2 so on...)
  $GWIPx = gateway ip address (ex. GWIP1=10.1.1.1, GWIP2=10.1.2.1 so on...)

If the izping daemon script is installed into /etc/init.d/, izbalancing will use it to make automatic failover and recovery of lines, checking the ip addresses specified into VERIFY_HOSTS and FAILOVER_HOSTS variables