Juniper JUNOSE 11.2.X BGP AND MPLS, Configuration Manual

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They must also be able to originate and terminate MPLS LSPs. (See “Configuring MPLS”
on page 275, for more information.)
P routers connect directly to PE routers or other P routers and do not connect directly to
customer sites. These routers must be able to switch MPLS LSPs—that is, they function
as MPLS label-switching routers (LSRs) and might function as label edge routers (LERs).
Running BGP-4 on the P routers is not necessary to be able to exchange routing
information for VPNs. You might run BGP-4 on the core routers for other reasons, such
as exchanging routing information for the public Internet or implementing route reflectors.
The P routes do not need to contain any information about customer sites.
PE routers communicate with customer sites through a direct connection to a customer
edge (CE) device that sits at the edge of the customer site. The CE device can be a single
host, a switch, or, most typically, a router. When the CE device is a router, it is a routing
peer of all directly connected PE routers, but it is not a routing peer of CE routers at any
other site. The link between the CE router and the PE router can employ any type of
encapsulation. Using MPLS is not necessary. In Figure 69 on page 387, each PE router
connects to multiple CE routers and at least one P router. Although only one customer
site is shown, each CE router lies within a customer site.
Figure 69: BGP/MPLS VPN Scenario
A customer site is a network that can communicate with other networks in the same
VPN. A customer site can belong to more than one VPN. Two sites can exchange IP
packets with each other only if they have at least one VPN in common.
387 Copyright © 2010, Juniper Networks, Inc.
Chapter 6: Configuring BGP-MPLS Applications