Explanation/Reference:
Section: Considerations for Expanding an Existing Network Explanation
Explanation:
You should issue the traceroute vrf boson 123.45.67.90 command to examine the path that packets take to reach the customer edge (CE) router from the provider edge (PE) router in this scenario. A virtual routing and forwarding (VRF) instance is the fundamental component of many virtual networking technologies and provides a mechanism for a single network device to maintain multiple, isolated routing tables. Because a VRF instance on a network device is isolated from other VRF instances on the same device, multiple VRF instances can be configured with the same IP address information. PE routers are typically configured with multiple VRF instances to isolate customer traffic and to mitigate IP addressing conflicts without requiring changes in the customer topology.
CE routers are typically not configured with VRF instances and are not aware of the VRF instances configured on PE routers. The PE interface associated with the VRF instance to which a CE router is connected is indistinguishable from a normal interface from the perspective of the CE router. VRF-aware network commands, such as ping and traceroute, on a device configured without any VRF instances, such as the CE router in this scenario, do not require any special parameters to identify the associated VRF instance. For example, when you use the traceroute command to examine the path that packets take from a CE router to a PE router, it is not necessary to specify the name of a VRF instance configured on the PE router.
By contrast, a network command on a device configured with multiple VRF instances, such as the PE router in this scenario, must specify the VRF instance to which the command should be applied. You can specify a VRF instance name by using the vrf vrf-name parameter with the traceroute command on a Cisco router. For example, you could issue the traceroute vrf boson 123.45.67.90 command to test connectivity from the PE router to the CE router in this scenario. Without a specified VRF instance name, the PE router in this example would attempt to reach the CE router by using the global routing table and not the routing table specific to the VRF named boson.
When using the vrf keyword, the appropriate VRF instance name must be used in place of the vrf-name variable; otherwise, the command will produce an error message. For example, you could not issue the traceroute vrf 123.45.67.90 command to test the connectivity from the PE router to the CE router in this scenario, because that command is missing the VRF instance name.
You should not issue the traceroute boson command. The traceroute boson command would attempt to connect to a host named boson, not to a VRF instance named boson. The traceroute boson command would only work in this scenario if the host name boson
had been assigned to the IP address 123.45.67.89 in Domain Name System (DNS) and if the IP address were reachable through a route in the global routing table. There is nothing in this scenario to indicate that a host name of boson resolves to the IP address 123.45.67.89.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 4, VRF, p. 154
Cisco: Network VirtualizationPath Isolation Design Guide: Diagnostic Tools (Ping, Traceroute)