"mạng riêng ảo MPLS và RIP, bạn đã học được làm thế nào để thực hiện một VPN đơn giản bằng cách sử dụng RIPv2 là khách hàng giao thức định tuyến. Chương này thảo luận về OSPF là giao thức định tuyến động được sử dụng giữa các bộ định tuyến CE và PE. | n Chapter 6 MPLS VPNs and RIP you learned how to implement a simple VPN using RIPv2 as the customer routing protocol. This chapter dis- cusses OSPF as the dynamic routing protocol used between CE and PE routers. OSPF is a well-established protocol that is used by both service providers and enterprises. Given the unique challenges of facilitating proper path selection many extensions have been added to OSPF. This chapter explains the enhancements made to the OSPF hierarchy OSPF routing loop prevention and how OSPF operates and in an MPLS VPN network. This chapter covers everything that you ve seen so far. There s a lab at the end of this chapter that demonstrates all the necessary configuration steps for setting up a simple MPLS VPN using OSPF as the dynamic routing protocol between the CE and PE routers. MP-BGP and OSPF Open Shortest Path First OSPF is a popular routing protocol that is used by both enterprises and service providers. Officially RIPv2 OSPF and E-BGP are dynamic routing protocols supported by Cisco between PE and CE routers. In addition static routes can be configured instead of using a dynamic routing protocol. Static routes are discussed in Chapter 8 Advanced MPLS Topics. This chapter is devoted to OSPF. Before discussing OSPF and its operation for MPLS VPNs let s start with a review of OSPF. Copyright 2002 SYBEX Inc. Alameda CA MP-BGP and OSPF 263 A Review of OSPF OSPF is a hierarchical routing protocol that breaks a network into areas. All OSPF areas must be connected to the backbone area Area 0 . The entire OSPF network is called the OSPF domain. Figure illustrates a simple OSPF network. FIGURE A simple OSPF network Notice in Figure that the network is divided into three areas Area 0 Area 1 and Area 2. Area 1 and Area 2 are connected to Area 0 which is the OSPF backbone. For now just remember that in standard OSPF all the areas must be connected to Area 0. OSPF Router Types There are several OSPF router types that you .
