As we know,load-balancing with double-outlet can provide a alternate link when one of the link fault.
And,there are three common dual-outlet load-balancing.
1.dual-outlet with one is high-speed link and another is low-speed link,high-speed link act as main link,low-speed link act as cold backup.
2.dual-outlet with two different ISPs,and both of them are in used.Different users access internet use different ISP link.
3.dual-outlet with one ISP,but two links are using different bandwidth.Both links are in used to increase the total accessing bandwidth.
Within secnario one,there may be two ISPs,or only one ISP.
Whatever the number of ISP is,the configuration keeps same.
a) configure interface IP address or dialing configuration.
b) configure NAT on both interfaces.
c) configure default-route towards high-speed link,and float default-route towards low-speed link.
d) configure NQA or BFD track for speeding up link convergence.
mainly configuration
default-route:
ip route-static 0.0.0.0 0.0.0.0 x.x.x.x //default-route towards high-speed link without BFD/NQA
ip route-static 0.0.0.0 0.0.0.0 y.y.y.y preference 80 //default-route towards load- balancing link without BFD/NQA track.
NQA track:
BFD track:
Within secnario two,
a) configure interface IP address or dialing configuration.
b) configure NAT on both interfaces.
c) configure traffic-policy to distinguish different users for applying different destination-address.
mainly configuration:
NOTES: traffic-policy supports associating with NQA,command as below:
redirect ip-nexthop ip-address [ vpn-instance vpn-instance-name ] [ track { nqa admin-name test-name | ip-route ip-address { mask | mask-length } } ] [ post-nat ] [ discard ]
with secnario three,
a) configure interface IP address or dialing configuration.
b) configure NAT on both interfaces.
c) configure two default-routes with same preference,so that traffic will load balanced on both interfaces.
d) adjust load-balancing algorithm,adjust load-balancing based on source IP to prevent when accessing to the same external network resource,the source address is translated into different public address due to different exit port.
mainly configuration:
ip load-balance hash src-ip //set load-balancing based on source IP
int e0/0/0
load-balance bandwidth link_bandwidht //link_bandwidth is the specific bandwith value of the link.
load-balance unequal-cost enable
then restart this interface.
do the same configuration on another interface.
If you guys find any errors in this post,plz figure it out,and it's pleasure to see you sharing your thoughts~ 
