VRF Implementation Considerations

Chapter 1 About Cisco IP Solution Center

About MPLS VPNs

Figure 1-9 VRFs for Sites in Multiple VPNs

Site 1				Site 4
VPN A	Site 2	VPN B	Site 3	VPN C

ip vrf site1 rd 100:1

route-target export 100:1 route-target import 100:1

ip vrf site2 rd 100:2

route-target export 100:2 route-target import 100:2 route-target import 100:1 route-target export 100:1

Multihop MP-iBGP

PE1

PE2

ip vrf site3 rd 100:3

route-target export 100:2 route-target import 100:2 route-target import 100:3 route-target export 100:3

ip vrf site4 rd 100:4

route-target export 100:3 route-target import 100:3

VRF

for site 1

(100:1)

Site 1 routes Site 2 routes

Site 1

VRF

for site 2

(100:2)

Site 1 routes Site 2 routes Site 3 routes

Site 2

VRF

for site 3

(100:3)

Site 2 routes Site 3 routes Site 4 routes

Site 3

VRF

for site 4

(100:4)

Site 3 routes Site 4 routes

Site 4

28558

When implementing VPNs and VRFs, Cisco recommends you keep the following considerations in mind:

•A local VRF interface on a PE is not considered a directly-connected interface in a traditional sense. When you configure, for example, a Fast Ethernet interface on a PE to participate in a particular VRF/VPN, the interface no longer shows up as a directly-connected interface when you issue a show ip route command. To see that interface in a routing table, you must issue a show ip route

vrf vrf_name command.

•The global routing table and the per-VRF routing table are independent entities. Cisco IOS commands apply to IP routing in a global routing table context. For example, show ip route, and other EXEC-level show commands—as well as utilities such as ping, traceroute, and telnet—all invoke the services of the Cisco IOS routines that deal with the global IP routing table.

•You can issue a standard Telnet command from a CE router to connect to a PE router. However, from that PE, you must issue the following command to connect from the PE to the CE:

telnet CE_RouterName /vrf vrf_name

Similarly, you can utilize the Traceroute and Ping commands in a VRF context.

Cisco IP Solution Center, 3.0: MPLS VPN Management User Guide, 3.0

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