in what scenario ,client get more than a default-route when dhcp is in effect?

[admin_2]

in dhcp pool,input default-router ip1 ip2, i found, when the ip1 fail, the client's default-gateway can't switch ip2. so,why using default-router ip1 ip2 or more default router?

[#2]

All the default-router addresses should be passed down to the client, which should use them in decending order. Whether or not the client actually uses the other addresses is dependent on the client.