netsane is a set of scripts to easily configure and 
maintain route load balancing (of sorts) between 
disparate networks, easily define null routes, and 
mark specific traffic to flow out specific gateways.

Balancing requires iproute2 and specific kernel requirements:

 	CONFIG_IP_ADVANCED_ROUTER
  	CONFIG_IP_MULTIPLE_TABLES
   	CONFIG_IP_ROUTE_MULTIPATH

Load balancing WILL NOT WORK WITHOUT THESE KERNEL ADDITIONS. Netsane
has been tested with iproute2-ss010824.

netsane v1 works for -2- gateways.

-----------------

FEATURES:	

* Use of multipath gateways (Failed lines *should* be detected transparently)
* Can detect/workaround 'dead' gateway iproute2 bug
* Ability to add blackholed destinations
* Ability to tie specific destinations to specific routes
* Ability to mark outgoing packets to use specific routes

-----------------

BUGS: 		

There are reports of the iproute2 tools being oddly broken in 2.4.x, depending
on a wide variety of factors (GCC build, iptools version, etc).
		
Netsane *DOES* try a basic workaround for this problem (which is
marking one of the gateways as 'dead') by adding the first gateway
twice (which seems to solve things on my test workstation).

It looks something like this:

$ip r sh

default
        nexthop via x.x.x.x  dev eth0 weight 1 dead
		nexthop via x.x.x.x  dev eth0 weight 1
		nexthop via y.y.y.y  dev eth1 weight 1 pervasive
						
This may not be sufficent in your case, and I have little
recommendation other than to track down a patch for iproute2 and
hope for the best. I do -not- experience this problem using
iproute2-ss010824 and GCC 3.3.1

Of special note is that netsane DOES NOT ASSUME you have patched
your kernel with the patches available at http://www.ssi.bg/~ja/
(you may do well to do so). 

-----------------

CAVEATS: 	

Netsane CANNOT provide ANY form of true redundancy nor true failover. It
simply affords a relatively easy way to configure multipath routing.

As Julian Anastasov notes (the author of a series of patches related
to routing), Linux 'out of the box' will not detect ARP neighbor failures. 
Proper detection of upstream failure should be achieved via scripts which 
adjust the routing table in the event of upstream failure. 

Without such mechanisms, non-local failures will NOT be detected,
and your system will happily continue to send packets down
the failed (upstream) route. In other words, while pulling the cable
from one interface will automagically cause the kernel to use the
other interface, the standard multipath mechanisms will NOT 
detect dead upstreams past the local network.

IP Aliases

Netsane does not play nice with 'old style' ip aliases (e.g., eth0:1).
Partly this is due to the nature of iproute2 (there are other mechanisms
for adding additional addresses to devices), and that netsane tries to
set 'sane' defaults for route assignments per *device* (to ensure
policy routes are tied to specific devices, which are attached to
specific networks).

-----------------

USAGE:

Here are some suggestions:

Before RUNNING THIS SCRIPT MAKE A COPY OF /etc/iproute2/rt_tables
The script expects this 'clean' copy as /etc/iproute2/rt_tables_SANE

1)	Configure your network 'normally' - DO NOT add more than one
	default gateway (i.e., only set one of the interfaces to have
	a default gateway).

2)	Create a directory for netsane to reside (I like /etc/netsane)

3) 	Edit /etc/netsane/netsane.conf

4)	If you've decided to use something OTHER THAN /etc/netsane,
	edit netsane.sh (so that it can find netsane.conf)

5)	Update your rc scripts to run /etc/netsane/netsane.sh AFTER ALL
	OTHER NETWORKING scripts have run. WARNING: many distributions 
	WILL NOT RUN scripts linked within if-up.d/ unless you strip
	the suffix (i.e., use ln -s /etc/netsane/netsane.sh netsane)

6)	If you have networks you wish to blackhole, add them to
	/etc/netsane/blackhole

-----------------

RUNTIME OPTIONS

Netsane accepts the following options:

        -f|stop    ............... (flush) remove multiroutes
        init|start ............... (init) start netsane
        restart    ............... (restart) restart netsane
        -dip1      ............... (drop ip1gw) remove IP1 gateway
        -dip2      ............... (drop ip2gw) remove IP2 gateway
        -h|help    ............... (help) print usage