Wide Area Networks Questions and Answers

Answer: C

Correct answer: An IP address on the physical interface

With point-to-point subinterfaces each subinterface is a separate network and carries its own IP address, so the physical interface must not have one. What the physical interface does carry is the Frame Relay encapsulation; the subinterfaces then take the point-to-point type and each is assigned its local DLCI with frame-relay interface-dlci.

Answer: B

Correct answer: frame-relay map

Inverse ARP normally discovers which DLCI reaches which remote IP address automatically. Where it is not operating - because it has been disabled, or the far end does not support it - the mapping must be entered by hand with frame-relay map ip <address> <dlci>, optionally with the broadcast keyword so that routing updates are replicated onto that circuit.

Answer: D

Correct answer: Cable

HFC stands for hybrid fibre-coaxial, the plant a cable operator uses: fibre from the head end to a neighbourhood node, then coaxial cable to the individual premises. It is specific to cable broadband. DSL runs over the existing telephone pair, and Frame Relay and a dedicated T1 are carrier services with no such plant of their own.

Answer: C

Correct answer: PPPoE

PPPoE carries PPP frames inside Ethernet frames, which lets a provider keep PPP’s per-subscriber authentication, accounting, encryption and compression while delivering service over an Ethernet-style access network. It is the usual arrangement for DSL and fibre broadband, and PPPoA is its counterpart where the access link is ATM.

Answer: D

Correct answer: PPP

Three requirements point to PPP together: it carries multiple routed protocols over the same link, it authenticates with PAP or CHAP, and it supports callback, which is what turns a long-distance charge into one the company controls. HDLC in its Cisco form is proprietary and offers neither authentication nor multiprotocol negotiation, Frame Relay is not a dial-up technology, and 802.1 is not a WAN protocol at all.

Answer: A

Clocking on a serial interface is always provided by the CSU/DSU (DCE device). However, if you do not have a CSU/DSU in your nonproduction test environment, then you need to supply clocking with the clock rate command on the serial interface of the router with the DCE cable attached.

Answer: C

Correct answer: 3, 4 and 5

HDLC, Frame Relay and PPP are all serial encapsulations, and HDLC is the Cisco default. Ethernet and Token Ring are LAN technologies with their own interface types and cannot be configured on a serial line - the encapsulation must match the physical medium and the far end.

Answer: C

Correct answer: debug ppp authentication

CHAP is an authentication method within PPP, so the debug that shows the exchange - the challenge, the response and the success or failure - is debug ppp authentication. There is no debug chap command, and show interface serial 0 reports the line and protocol state without showing the negotiation that produced it.

Answer: C

Correct answer: 3, 4 and 5

The question mark lists the available keywords, which are lmi, pvc and map - the local management interface statistics, the state and counters of each virtual circuit, and the mappings of protocol address to DLCI. There is no show frame-relay dlci or neighbors; the DLCI information appears within the pvc and map output.

Answer: A

If you have a serial port configured with multiple DLCIs connected to multiple remote sites, split horizon rules, stop route updates received on an interface from being sent out the same interface. By creating subinterfaces for each PVC, you can avoid the split horizon issues when using Frame Relay.