BGP "TRAFFIC SHAPING" EXAMPLE

BGP is not intended to be used for traffic balancing, it is used to find
best path. However, let's assume that you have two ISP-s (two AS), and that
you don't want all packages to go over best path in fact let's say that you
want to have more balanced traffice. Here is example how it can be done
using prepends:



!
router bgp MY_AS_NUMBER
 network my_network/netmask
 neighbor neighbor1_ISP_peer_ip remote-as neighbor1_ISP1_AS
 neighbor neighbor1_ISP_peer_ip soft-reconfiguration inbound
 neighbor neighbor1_ISP_peer_ip prefix-list bogus in
 neighbor neighbor1_ISP_peer_ip route-map ISP1_ROUTE_MAP out
 neighbor neighbor2_ISP_peer_ip remote-as neighbor2_ISP2_AS
 neighbor neighbor2_ISP_peer_ip soft-reconfiguration inbound
 neighbor neighbor2_ISP_peer_ip prefix-list bogus in
 neighbor neighbor2_ISP_peer_ip route-map ISP2_ROUTE_MAP out
!
! put this if you don't want ISP1 to see ISP2 through you
!
ip as-path access-list no_transit permit ^$
ip as-path access-list no_transit deny .*
!
ip prefix-list pl100 seq 5 permit my_network/netmask
ip prefix-list pl100 seq 10 deny any
ip prefix-list pl101 seq 5 permit my_network/netmask
ip prefix-list pl101 seq 10 deny any
!
route-map ISP2_ROUTE_MAP permit 10
 match as-path no_transit
 match ip address prefix-list pl101
 set as-path prepend MY_AS_NUMBER MY_AS_NUMBER ... MY_AS_NUMBER 
!
route-map ISP1_ROUTE_MAP permit 20
 match ip address prefix-list pl100
 match as-path no_transit
!

In this example you are prepending your AS to ISP2. Therefore for BGP it
looks like ISP1 is closer to you then ISP2 so you get more incoming traffic
from ISP1.  There are other ways but this one is most simple solution.