Frame Relay

Question 1

Which protocol uses dynamic address mapping to request the next-hop protocol address for a specific connection?

A. Frame Relay inverse ARP
B. static DLCI mapping
C. Frame Relay broadcast queue
D. dynamic DLCI mapping

Answer: A

Normal (Ethernet) ARP Request knows the Layer 3 address (IP) and requests for Layer 2 address (MAC). On the other hand, Frame Relay Inverse ARP knows the Layer 2 address (DLCI) and requests for Layer 3 address (IP) so we called it “Inverse”.

Question 2

What is the default OSPF hello interval on a Frame Relay point-to-point network?

A. 10
B. 20
C. 30
D. 40

Answer: A

When saying “Frame Relay point-to-point” network, it means “Frame Relay subinterfaces” run “point-to-point”. Notice that Frame Relay subinterfaces can run in two modes:
+ Point-to-Point: When a Frame Relay point-to-point subinterface is configured, the subinterface emulates a point-to-point network and OSPF treats it as a point-to-point network type
+ Multipoint: When a Frame Relay multipoint subinterface is configured, OSPF treats this subinterface as an NBMA network type.

And there are 4 network types which can be configured with OSPF. The hello & dead intervals of these types are listed below:

Network Type Hello Interval (secs) Dead Interval (secs)
Point-to-Point 10 40
Point-to-Multipoint 30 120
Broadcast 10 40
Non-Broadcast 30 120

Therefore the default OSPF hello interval on a Frame Relay point-to-point network is 10 seconds.

Question 3

A company has their headquarters located in a large city with a T3 frame relay link that connects 30 remote locations that each have T1 frame relay connections. Which technology must be configured to prevent remote sites from getting overwhelmed with traffic and prevent packet drops from the headquarters?

A. traffic shaping
B. IPsec VPN
C. GRE VPN
D. MPLS

Answer: A

Traffic shaping should be used when:
+ Hub site (headquarter) has much faster speed link than the spokes (remote sites). In this case we need to rate-limit the hub site so that it does not exceed the remote side access rate
+ Hub site has the same speed link as the spokes. For example both the headquarter and the spokes use T1 links. In this case, we need to rate-limit the remote sites so as to not overrun the hub.

An example of configuring traffic shaping is shown below:

interface Serial0/1
encapsulation frame-relay
frame-relay traffic-shaping
!
interface Serial0/1.10 point-to-point
ip address 10.10.10.10 255.255.255.0
frame-relay interface-dlci 10 class my_traffic_shaping
!
map-class frame-relay my_traffic_shaping
frame-relay adaptive-shaping becn //Configure the router to respond to frame relay frames that have the BECN bit set
frame-relay cir 128000 //Specify the committed information rate (CIR) for a Frame Relay virtual circuit
frame-relay bc 8000 //Specify the committed burst size (Bc) for a Frame Relay virtual circuit.
frame-relay be 8000 // Specify the excess burst size (Be) for a Frame Relay virtual circuit.
frame-relay mincir 64000 // Specify minimum acceptable CIR for a Frame Relay virtual circuit.

Question 4

On which two types of interface is Frame Relay switching supported? (Choose two)

A. serial interfaces
B. Ethernet interfaces
C. fiber interfaces
D. ISDN interfaces
E. auxiliary interfaces

Answer: A D

Question 5

In which two ways can split horizon issues be overcome in a Frame Relay network environment? (choose two)

A. Configuring one physical serial interface with Frame Relay to various remote sites.
B. Configure a loopback interface with Frame Relay to various remote sites.
C. Configuring multiple subinterfaces on a single physical interface to various remote sites.
D. Enabling split horizon.
E. Disabling split horizon.

Answer: C E

Question 6

Refer to the exhibit.

Router 1 cannot ping router 2 via the Frame Relay between them. Which two statements describe the problems? (Chooses two)

A. Encapsulation is mismatched.
B. Frame Relay map is configured.
C. DLCI is active.
D. DLCI is inactive or deleted.
E. An access list is needed to allow ping.

Answer: A D

Question 7

How should a router that is being used in a Frame Relay network be configured to keep split horizon issues from preventing routing updates?

A. Configure a separate subinterface for each PVC with a unique DLCI and subnet assigned to the subinterface.
B. Configure each Frame Relay circuit as a point-to-point line to support multicast and broadcast traffic.
C. Configure many subinterfaces in the same subnet.
D. Configure a single subinterface to establish multiple PVC connections to multiple remote router interfaces.

Answer: A

Each subinterface is treated like a physical interface so split horizon issues are overcome.

Question 8

Which value does Frame Relay use to identify a connection between a DTE and DCE?

A. DLCI
B. IP address
C. MAC address
D. VLAN ID

Answer: A

Frame-relay uses data-link connection identifiers (DLCIs) to build up logical circuits. The identifiers have local meaning only, that means that their values are unique per router, but not necessarily in the other routers. For example, there is only one DLCI of 23 representing for the connection from HeadQuarter to Branch 1 and only one DLCI of 51 from HeadQuarter to Branch 2. Branch 1 can use the same DLCI of 23 to represent the connection from it to HeadQuarter. Of course it can use other DLCIs as well because DLCIs are just local significant.

By including a DLCI number in the Frame Relay header, HeadQuarter can communicate with both Branch 1 and Branch 2 over the same physical circuit.

Question 9

Which two statements about configuring Frame Relay point-to-multipoint connections are true? (Choose two)

A. They ignore the broadcast keyword in the frame-relay DLCI mapping
B. They require the same DLCI on each side of the link
C. Changing a point-to-multipoint subinterface to a different type requires the interface to be deleted and recreated
D. They require the frame-relay mapping command to be configured
E. They require inverse ARP

Answer: D E

Frame Relay point-to-multipoint requires inverse ARP (which is enabled by default). It requires the frame-relay mapping command to be configured also. For example: R1(config-if)#frame-relay route 102 interface Serial0/1 201.

Question 10

Which two statements about Frame Relay LMI autosense are true on a router? (Choose two)

A. It requires the LMI type to be explicitly configured
B. It operates on Frame Relay DTE interfaces
C. It operates on Frame Relay DCE interfaces
D. It operates when the line is up but the line protocol is down
E. It requires the line protocol to be up

Answer: B D

LMI autosense is automatically enabled in the following situations:
+ The router is powered up or the interface changes state to up
+ The line protocol is down but the line is up
+ The interface is a Frame Relay DTE
+ The LMI type is not explicitly configured on the interface