HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual page 698

IP Routing—Configuring RIP, OSPF, BGP, and PBR
Configuring BGP
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For example, your organization uses private networks 192.168.1.0 /24 through
192.168.16.0 /24. You could configure one prefix list to allow the advertisement
of networks 192.168.1.0 /24 through 192.168.7.0 /24:
ProCurve(config)# ip prefix-list ISP1Out seq 1 permit 192.168.0.0/21 ge 24 le 24
You would then apply the prefix list to routes advertised to one BGP neighbor:
ProCurve(config)# router bgp 1
ProCurve(config-bgp)# neighbor 10.1.1.1
ProCurve(config-bgp-neighbor)# prefix-list ISP1Out out
You could then configure another prefix list that allows the second half of the
networks and apply the list to the second neighbor:
ProCurve(config)# ip prefix-list ISP2Out seq 1 permit 192.168.8.0/21 ge 24 le 24
ProCurve(config)# router bgp 1
ProCurve(config-bgp)# neighbor 10.2.2.2
ProCurve(config-bgp-neighbor)# prefix-list ISP2Out out
Load Balancing Outgoing Traffic by Preventing an Interface from
Learning Specific Routes. In a multihomed network, you can configure
load balancing for outbound traffic by controlling which external routes each
router or router interface learns. Divide all external networks into the number
of connections that your network has to the Internet. Assign a section of these
external networks to each BGP interface and filter out all other traffic on that
interface.
Customer
Network 1
Figure 13-19. Load Balancing Outgoing Traffic
Router A
Network 2
ISP 1
ISP 2