Example Prefix List Configuration; Route Exchange; Configuring Route Maps: Creating More Complex Policies; For Route Exchange - HP 7102dl - ProCurve Secure Router Configuration Manual

IP Routing—Configuring RIP, OSPF, BGP, and PBR
Configuring BGP
15-88

Example Prefix List Configuration

Router A in AS 1 connects to the Internet. It uses a default route for typical
Internet traffic, but needs routes to the private networks at a remote VPN site.
Each site in the VPN uses addresses in the 10.1.0.0 /16 range. To minimize the
number of routes routers must learn, the organization has decided that each
site should advertise its range of subnets as a 20-bit network. For example,
the local site uses subnets in the 10.1.0.0 /20 range, Site 2 uses subnets in the
10.1.16.0 /20 range, and so forth.
Router A connects to two ISPs. Your organization would also filter BGP
updates so that the router does not advertise external routes from one ISP to
the other, turning your private network into a thoroughfare between them.
You should configure filters to advertise only the local routes and accept only
the remote private routes as follows:
ProCurve(config)# ip prefix-list FilterOut seq 1 permit 10.1.0.0/20
ProCurve(config)# ip prefix-list FilterIn seq 1 permit 10.1.0.0/16 ge 20 le 20
ProCurve(config)# router bgp 1
ProCurve(config-bgp)# neighbor 1.1.1.1
ProCurve(config-bgp-neighbor)# prefix-list FilterOut out
ProCurve(config-bgp-neighbor)# prefix-list FilterIn in
ProCurve(config-bgp-neighbor)# exit
ProCurve(config-bgp)# neighbor 2.2.2.2
ProCurve(config-bgp-neighbor)# prefix-list FilterOut out
ProCurve(config-bgp-neighbor)# prefix-list FilterIn in

Configuring Route Maps: Creating More Complex Policies

for Route Exchange

Route maps allow you to configure more complex policies than do prefix lists.
You associate a route map with each neighbor to define which routes the BGP
interface can advertise to and accept from that neighbor.
However, as well as filtering routes according to network address and prefix
length, you can also filter routes according to their AS path and BGP commu-
nity. (A BGP community is a group of routes to which a BGP router applies
the same policies. You will learn more about communities in "Configuring a
Community List" on page 15-90 and "Placing a Route in a Community: Request-
ing a Neighbor to Advertise a Route to Certain Peers Only" on page 15-97.)