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428 Chapter A: Answers to the "Do I Know This Already?" Quizzes and Q&A Sections
17
Users have reported issues with network reachability. What command could be utilized to
view the status of PVCs?
show frame-relay pvc
18
Write out a basic Frame Relay configuration including two point-to-point subinterfaces
off of Serial 0, using IP only. The DLCI for Serial 0.1 should be 24 and for Serial 0.2, the
DLCI should be 95.
Router(config)#interface serial 0
Router(config-if)#encapsulation frame-relay
Router(config-if)#interface serial 0.1 point-to-point
Router(config-if)#ip address 10.1.1.1 255.255.255.0
Router(config-if)#frame-relay interface-dlci 24
Router(config-if)#interface serial 0.2 point-to-point
Router(config-if)#ip address 10.1.2.1 255.255.255.0
Router(config-if)#frame-relay interface-dlci 95
19
Create the same configuration from Question 18, but use multipoint interfaces instead.
Router(config)#interface serial 0
Router(config-if)#encapsulation frame-relay
Router(config-if)#interface serial 0.1 multipoint
Router(config-if)#ip address 10.1.1.1 255.255.255.0
Router(config-if)#frame-relay map ip 10.1.1.2 24 broadcast
Router(config-if)#interface serial 0.2 multipoint
Router(config-if)#ip address 10.1.2.1 255.255.255.0
Router(config-if)#frame-relay map ip 10.1.2.2 95 broadcast
20
Once the router has decreased throughput due to BECN requests, how long must it wait
prior to increasing throughput once again?
The router must wait for 16 time intervals (usually about two seconds) of receiving no
BECNs before increasing throughput.
21
Increasing throughput once every 16 time intervals can mean that some time passes before
CIR speed is regained. How can the router be configured to force the speed back to CIR
immediately after the congestion has cleared?
Set the Be to 7
Ч Bc. The Bc is the amount of data sent in a time interval, usually CIR ч
8. The Be is the amount of excess data allowed to be sent during the first interval with
credit. Because BECN has backed the speed down, a credit builds for each time interval.
If CIR is 64,000, Bc is 8000. If Be is set to 7
Ч Bc, it will be 56,000. Once 16 time intervals
have passed, the throughput bursts to CIR immediately (Bc = 8000) + (Be = 56,000)
ч 16
= 4000 bps per time interval. Successful passage of 16 time intervals with no BECN sends
the value to 64,000 bps immediately rather gradually.
22
What happens to LMI traffic if the command no keepalive is issued on the router
interface?
LMI traffic ceases to cross the link.