Panasonic NN46240-710 - Manual (Page 83)

3 BGP/MPLS IP VPN troubleshooting
Nortel Secure Router 8000 Series
_________ Troubleshooting - VPN
Figure 3-2 BGP/MPLS VPN instances
VPN1 VPN1
Figure 3-2 shows a BGP/MPLS VPN topology. In a basic BGP/MPLS VPN network topology,
a service operator provides BGP/MPLS VPN service to multiple enterprises. Two PEs connect
with four different customer sites.
Routing information exchange
As shown in Figure 3-2, the CE1-bound interface or subinterface on PE1 is associated with
VRF1. When CE1 advertises the route with the prefix of 10.1.0.0/16 to PE1, PE1 adds this route
to VRF1.
The PE1 marks 10.1.0.0/16 with the private and public label successively, and sends it to PE2.
The PEs uses Multiple Protocol IBGP (MP-IBGP) to carry VPN Target (VT) and Route
Distinguisher (RD) information and use the loopback address as the next hop of the IBGP route.
This process resolves the problem of the repeated address realm and simplifies the route
filtering.
By using the RD and VPN-IPv4 address family (defined in RFC 1918), RFC2547bis supports
the overlapping address space. By using the technique of BGP extension attribute-based
filtering, RFC2547bis implements forced route exchange between PE routers.
Upon receiving the routing information from PE1, PE2 filters it according to the existing BGP
extension attribute. The PE2 also determines whether to add the 10.1.0.0/16 route to VRF1.
Once the 10.1.0.0/16 route is added to VRF1, PE2 will advertise it to CE2.
LSP establishment
To transfer VPN routes transparently from one PE to another, you can use the Label
Distribution Protocol (LDP) or Reservation Protocol (RSVP) to establish LSPs on the network
of the service operator. To ensure interoperation between devices from different vendors, all PE
and P routers should support LDP. The LSP based on LDP and that based on RSVP establish
between a pair of PE routers. You can establish one LSP or multiple parallel LSPs between PE
3-4 Nortel Networks Inc. Issue 5.3 (30 March2009)