Vrf And Mpls - HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual

IP Routing—Configuring RIP, OSPF, BGP, and PBR
Configuring BGP
13-66
With static routing, you configure a default route on the local router to the ISP
router. The ISP manually configures routes to the private sites on its edge
routers directly connecting to these sites.
RIP v2 runs on the network between the private router and the ISP router. The
ISP edge routers then redistribute the static or RIP routes into BGP, which
runs on the ISP network. The ISP tunnels the routes through its network to
the remote sites, as it does with those discovered by eBGP.
Static routing and RIP are simple to configure, have low overhead, and are
well suited for medium-to-small networks with only one connection to an ISP.
However, BGP offers several advantages, particularly in more complex envi-
ronments:
Unlike routers using static routing, routers running BGP can automati-
cally respond to downed connections and changes in network topology.
Your organization can change its IP addressing without notifying your ISP.
(RIP v2 also offers this advantage.)
BGP can handle complex applications in which the private network
connects to multiple ISP routers or multiple ISPs. You can configure BGP
to balance loads among these connections.
BGP is the native protocol run by ISPs, which decreases problems caused
by redistributing static or RIP routes into BGP.
BGP is policy based, so you maintain tight control over the routes trans-
mitted and accepted.

VRF and MPLS

An ISP uses Virtual Routing and Forwarding (VRF) to separate one customer's
routes from another's and Multiprotocol Label Switching (MPLS) to ensure
that the routes reach only the authorized remote sites. Without VRF, customers
could not transmit private network routes between remote sites: the ISP
routers would have no way of knowing which route belonged to which
customer.
For example, in Figure 13-15 an ISP router connects to Customer A and
Customer B, both of whom use the network address 10.1.1.0 /24. The ISP
router must be able to associate one 10.1.1.0 /24 with the public address for
Customer A and the other with Customer B.
On the ISP edge router, routes are first separated by the physical or logical
interface on which they arrive. The router then stores routes from each
customer in a separate VFR routing table. Different customers' routing tables
cannot mix.