770 Appendix A: Answers to the "Do I Know This Already?" Quizzes and Q&A Sections
14
What benefit related to routing protocols can be gained by using subinterfaces with a
partial mesh?
Split horizon issues are avoided by treating each VC as a separate interface. Split horizon
is still enabled; routing loops are not a risk, but all routes are learned.
15
Can PPP perform dynamic assignment of IP addresses? If so, is the feature always
enabled?
PPP's IPCP protocol can assign an IP address to the device on the other end of the link.
This process is not required. PPP usually does address assignment for dial access, for
example, when a user dials an Internet service provider.
16
Create a configuration to enable PPP on serial 0 for IP and IPX. Make up IP and IPX
Layer 3 addresses as needed.
interface serial 0
ip addr 1.1.1.1 255.255.255.0
ipx network 1
encapsulation ppp
encapsulation ppp is all that is needed for PPP. Having IP and IPX enabled causes PPP
to enable the control protocols for each.
17
Create a configuration for Router1 that has Frame Relay VCs to Router2 and Router3
(DLCIs 202 and 203, respectively) for Frame Relay on Router1's serial 1 interface. Use
any IP and IPX addresses you like. Assume that the network is not fully-meshed.
interface serial 1
encapsulation frame-relay
interface serial 1.1 point-to-point
ip address 168.10.1.1 255.255.255.0
ipx network 1
frame-relay interface-dlci 202
interface serial 1.2 point-to-point
ip address 168.10.2.1 255.255.255.0
ipx network 2
frame-relay interface-dlci 203
This is not the only valid configuration given the problem statement. However, because
there is not a full mesh, then point-to-point subinterfaces are the best choice. Cisco
encapsulation is used by default. The LMI type is autosensed.
18
What show command will tell you the time that a PVC became active? How does the
router know what time the PVC became active?
The show frame-relay pvc command lists the time since the PVC came up. The router
learns this from an LMI message.
apA.fm Page 770 Monday, March 20, 2000 5:24 PM