Answers to Review Questions 259

Answers to Review Questions

1.D. A route target is 64 bits long, but only 48 bits of it are configurable.

2.A. For simple VPNs, the route distinguisher and route target values are usually the same.

3.B. To configure only an import route target, you use the routetarget import number command.

4.C. The address-family vpnv4 command is used to configure

MP-BGP, not a routing context.

5.A. ISDN is a Layer 1 VPN technology. Additional technologies at this layer are T1, E1, and SONET.

6.C. IPSec is a Layer 3 VPN technology. An additional technology at this layer is a GRE tunnel.

7.B. Frame Relay is a Layer 2 VPN technology. Additional technologies at this layer are ATM and X.25.

8.B. The command to view the VRF routing table is show ip route vrf vpn_name.

9.B, C. Just like the route distinguisher, the two acceptable ways of configuring a route target is 16-bit:32-bit or 32-bit:16 bit.

10.B. MP-BGP neighbors need to be activated.

11.C. Redistribution for a VRF is configured under address-family ipv4 vrf vpn_name.

12.B. Redistribution for a VRF is configured under address-family ipv4 vrf vpn_name.

13.B. If you use the show ip route command, you see the global routing table. To verify that a route is being learned from a CE router, you want to look at the routing table for the VRF. The command to view the VRF routing table is show ip route vrf vpn_name.

14.A, C. IPSec and GRE are Layer 3 VPN technologies. Frame Relay is a Layer 2 VPN technology, and ISDN is a Layer 1 VPN technology.

260Chapter 6 MPLS VPNs and RIP

15.A. To view the global routing table on a PE, use the show ip route command.

16.D. To associate an interface with a VRF, use the command ip vrf forwarding vpn_name.

17.C. Once an interface is associated with a VRF, it loses its IP address and must be reconfigured.

18.B. Routing tables are well isolated with MPLS VPNs. The CE routers participating in the VPN do not learn any service provider backbone routes.

19.A. The easiest way to verify that a VPN works is to ping from one CE device to another. If the ping works, you know that VRFs, redistribution, etc. are configured properly.

20.C. In this example, RIP routes are being redistributed into MP-BGP. The original RIP route is received by another MP-BGP router and added to the VRF as a (B) route because it was learned through MP-BGP.