Brief: CCNA exam requires a good understanding of WAN concepts, terminology, and implementation using Cisco routers. We have given a few multiple choice questions to gauge your preparedness (yourself) of the subject before taking the exam!
Q1: Cisco IOS supports MPPC (Microsoft Point-to-Point Compression algorithm) on one of the following encapsulation types. Choose the correct one.
| A. HDLC B. LAPB C. PPP D. Frame-Relay | |
Ans.: C
Compression algorithms supported by Cisco IOS are:
| Encapsulation Type | Compression type supported by Cisco IOS |
| HDLC | STAC |
| LAPB | STAC, Predictor |
| PPP | STAC, Predictor, MPPC |
| Frame-Relay | STAC, FRF.9 |
PPP is supported by STAC, Predictor, and MPPC. Compression algorithms supported by Frame-Relay for payload compression are STAC, and FRF.9.
Q2. Which of the following is not an interface associated with a WAN connection?
| A. V.35 B. EIA 232 C. EIA 530 D. MSAU E. X.21 | |
Ans.: D
Expl.:
Typical WAN interfaces, that one come across frequently are:
EIA 232, EIA 449, EIA 530, V.35, and X.21. The Cisco router serial interface will be a 60-pin D-shell connector. This in turn is connected to service provider equipment, usually through a CSU/ DSU. Therefore, appropriate conversion cable need to be used when interfacing with a WAN device such a CSU/DSU. CSU/ DSU in turn is connected to the service provider through the cable supplied by the service provider.
Q3. Your router is connect to the service provider through a CSU/DSU. Choose appropriate interfaces used in correct order, starting from the router interface.
A. 60-pin D-shell connector --> EIA/TIA 232 --> RJ 45
B. 60-pin D-shell connector --> RJ 45 --> EIA/TIA 232
C. RJ 45 --> 60-pin D-shell connector --> EIA/TIA 232
D. EIA/TIA 232 --> RJ 45 --> 60-pin D shell connector
Ans.: A.
Expl.: Traditionally, the router interface on a serial link is a 60-pin D-shell connector. The CSU/DSU may have EIA/TIA 232 interface to the router. The CSU/DSU interface to the service provider could be RJ-11, RJ-45 etc.
Q4. Frame Relay protocol is based on fixed size frame length. In other words, the frame size can not be flexible.
| A. TRUE B. FALSE | |
Ans.: B (False)
Expl. Frame Relay is WAN protocol, that allows multi-access. Frame Relay works on packet-switched technology. Packet switched networks enable end stations to dynamically share the network medium and the available bandwidth. In Frame Relay, variable-length packets are used for more efficient and flexible data transfer.
Q5. Frame Relay supports which of the following?
| A. PVCs only B. SVCs only C. Both PVCs and SVCs D. None | |
Ans.C
Expl.: Frame Relay supports two type of virtual circuits (VCs):
1. Permanent Virtual Circuits (PVCs) _ these are permanently established connection that are used for frequent and consistent data transfers between DTEs across a Frame Relay cloud.
2. Switched Virtual Circuits (SVCs) _ these are temporary connections used in situations requiring only occassional data transfers between DTEs across Frame Relay cloud.
The terms "Call Setup", "Data Transfer", "Idle", and "Call Termination" are associated with SVCs. Frame Relay SVCs are not widely supported by manufacturers.
Q6. Frame Relay DLCIs must be unique in a Frame Relay network.
| A. TRUE B. FALSE | |
Ans.: B
Expl.: DLCI stands for Data-Link Connection Identifier. Frame Relay DLCIs have local significance, which means that the values themselves are not unique in the Frame Relay WAN. DLCIs must be unique on a given access link, i.e. the physical channel on which they reside.
Q7. Which of the following are reference points relevant to ISDN? [Select 2].
| A. T B. U C. V D. S | |
Correct answer: A,B,D
Explanation:
ISDN uses four different reference points to define logical interfaces:
1. R-reference point: Defines the reference point between non-ISDN compatible devices and a Terminal Adapter (TA).
2. S-reference point: Defines the reference point between user terminals and an NT2.
3. T-reference point: Defines the reference point between NT1 and NT2.
4. U-reference point: Defines the reference point between NT1 devices and line-termination equipment in a carrier network.
The flow of reference points are:
[TE2] ---R--->[TA]---S/T--->[NT1]--->U--->to carrier
[TE2]--->R--->[TA]--->S--->[NT2]--->T--->[NT2]--->to carrier
Q8. A frame is received at the destination router over Frame Relay network with FECN bit value set to 1. What does this indicate?
A. That there is traffic congestion in the direction of source to destination.
B. That there is traffic congestion in the direction of destination to source.
C. That there is no traffic congestion in the direction of source to destination.
D. That there is no traffic congestion in the direction of destination to source.
Ans.: A
Expl.: Frame Relay has two types of congestion notification mechanisms:
FECN: Forward-Explicit Congestion Notification, and
BECN: Backward-Explicit Congestion Notification.
If the network is congested in the direction of source to destination, FR switches set the value of the frames FECN to 1(one). DTE devices may implement flow control based on this information. FR switches set the value of BECN bit to 1 (one) in frames traveling in the opposite direction of frames with their FECN bit set. This will enable to DTE device to initiate appropriate flow control in the direction in which the frame has arrived.
