linux routing with multiply isp

Hi,

I have a linux box connected to a local lan. the ip address is
192.168.1.254. This is the default gateway for the lan. Also I have
to broadband connections that has routers. 1. Airtel 192.168.1.1 and 2
VSNL 192.168.1.9. My aim is that if either one of the lines go down I
want the other to take over. All connections are connected to a switch
which includes tbe broadband connections. My routing table is

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use
Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0
eth0
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0
eth1
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0
lo
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0
eth0
0.0.0.0 192.168.1.9 0.0.0.0 UG 0 0 0
eth0
0.0.0.0 192.168.1.254 0.0.0.0 UG 0 0 0
eth0

Right now if I switch off airtel it takes time to switch over the vsnl.
If I put back airtel and switch off vsnl it it still searches for
vsnl. If I use ip route flush cache. Then it work. Is there a way to
do this automatically.

I also run a local dns for the lan.

Regards

Adrian