Router load balancing

[bahamas68]

Background:
We have a router running bgp, and two t1 going to two different ISPs. That way if one T1 goes down, we're not without internet coverage. However, we are in the process of changing our connection to having one T1 going to one ISP, and a 10mbps ethernet connection going to the other isp which is located here on campus.
I have two questions:
1. How do we configure the router so that if the serial T1 goes down the Ethernet picks up, and vice versa?
2. How do I setup some type of load balancing so that the load is equally shared, or to send most of the traffic on the ethernet interface and about 30 percent on the serial.
Thanks in advance for your answers.

 

[saleen351]

answer to question 1;
create a floating static route.
answer to question 2;
load-balancing can "only" occur if the cost are the same on both the links.
what you can do is create access-list with different subnets going out thru the 2 ISP.

 

[Vuti]

One of the best (but messy) ways I've found is to configure a scale of route-maps setting the weight to x according to the AS path length of inbound routes. This way all BGP routes with an AS path of (eg)two will be preferred by the one link due to higher weight. You can then set the other link to be the preferred route for all routes with an AS path of 3 etc etc until you get close to the required balanced traffic levels you are after.

router bgp 21422
no synchronization
bgp log-neighbor-changes
neighbor [ ISP1] remote-as xxx
neighbor [ ISP1] route-map AS-PATH-IN in
neighbor [ ISP2] remote-as xxx
neighbor [ ISP2] route-map AS-PATH-SEC-IN in
no auto-summary
!
ip as-path access-list 90 permit ^[0-9]*$
ip as-path access-list 91 permit ^[0-9]* [0-9]*$
ip as-path access-list 92 permit ^[0-9]* [0-9]* [0-9]*$
ip as-path access-list 93 permit ^[0-9]* [0-9]* [0-9]* [0-9]*$
ip as-path access-list 94 permit ^[0-9]* [0-9]* [0-9]* [0-9]* [0-9]*$
ip as-path access-list 95 permit ^[0-9]* [0-9]* [0-9]* [0-9]* [0-9]* [0-9]*$
ip as-path access-list 96 permit ^[0-9]* [0-9]* [0-9]* [0-9]* [0-9]* [0-9]* [0-9]*$
ip as-path access-list 97 permit ^[0-9]* [0-9]* [0-9]* [0-9]* [0-9]* [0-9]* [0-9]* [0-9]*$
ip as-path access-list 98 permit ^[0-9]* [0-9]* [0-9]* [0-9]* [0-9]* [0-9]* [0-9]* [0-9]* [0-9]*$
ip as-path access-list 99 permit ^
!
route-map AS-PATH-IN permit 10
match as-path 90
set weight 30
!
route-map AS-PATH-SEC-IN permit 10
match as-path 90
set weight 29
!
route-map AS-PATH-IN permit 11
match as-path 91
set weight 28
!
route-map AS-PATH-SEC-IN permit 12
match as-path 91
set weight 27

etc etc until you get to as-path 99