Here you will find answers to QoS Questions
Question 1
Which of these is a valid differentiated services PHB?
A. Guaranteed PHB
B. Class-Selector PHB
C. Reserved Forwarding PHB
D. Discard Eligible PHB
E. Priority PHB
B. Class-Selector PHB
C. Reserved Forwarding PHB
D. Discard Eligible PHB
E. Priority PHB
Answer: B
Question 2
Refer to the exhibit. When applying this hierarchical policy map on the on the tunned interface, you measure high jitter for traffic going through class 1234. What is the most likely cause of this jitter?
class-map match-all 1234 match ip precedence 5 class-map match-all 5555 match access-group 105 class-map match-all 5554 match access-group 104 policy-map tun-shap class class-default shape average 150000 300000 service-policy mark policy-map mark class 1234 priority 64 class 5555 set dscp af31 bandwidth remaining percent 50 random-detect dscp-based class 5554 set dscp af32 bandwidth remaining percent 25 random-detect dscp-based interface Tunnel 1 ip address 20.2.2.1 255.255.255.252 ip load-sharing per-packet load-interval 30 qos pre-classify tunnel source 4.4.4.1 tunnel destination 4.4.4.2 service-policy output tun-shap access-list 104 permit ip any host 5.5.5.4 access-list 105 permit ip any host 5.5.5.5
A. The configuration of a hierarchical policy map on a tunnel interface is not supported.
B. Class 5555 and class 5554 are both taking up 100% of the bandwidth, leaving nothing for class 1234.
C. The burst size for the traffic shaping is wrongly configured to 15000; this would require an interface capable of sending at 150Mb/s.
D. The burst size for the traffic shaping has been wrongly configured; it should be set as low as possible.
E. The burst size for the traffic shaping has been wrongly configured; it should be set as high as possible.
B. Class 5555 and class 5554 are both taking up 100% of the bandwidth, leaving nothing for class 1234.
C. The burst size for the traffic shaping is wrongly configured to 15000; this would require an interface capable of sending at 150Mb/s.
D. The burst size for the traffic shaping has been wrongly configured; it should be set as low as possible.
E. The burst size for the traffic shaping has been wrongly configured; it should be set as high as possible.
Answer: D
Question 3
Refer to the exhibit. When applying this policy map on the tunnel1 interface, you see packet loss for the TCP class starting at around 100000 b/s, instead of the configured 150000 b/s. What is the most likely cause of the discrepancy?
class-map match-any tcp
match protocol http
match protocol ftp
class-map match-all acl180
match access-group 180
policy-map police
class tcp
police 150000 1000 conform-action transmit exceed-action drop
class acl180
police 150000 conform-action set-prec-transmit 2 exceed-action set-prec-transmit 1 violate-action set-prec-transmit 0
interface Tunnel1
ip address 20.1.1.2 255.255.255.252
service-policy input police
load-interval 30
tunnel-source 4.4.4.2
tunnel destination 4.4.4.1
A. The violate-action command should not be configured.
B. The current configuration of the load-interval command on the tunnel interface is preventing proper policing calculations.
C. The burst size is too low.
D. Policing on tunnel interfaces is not supported.
E. The CIR keyword is missing in the policer.
B. The current configuration of the load-interval command on the tunnel interface is preventing proper policing calculations.
C. The burst size is too low.
D. Policing on tunnel interfaces is not supported.
E. The CIR keyword is missing in the policer.
Answer: C
Question 4
Refer to the exhibit. As a network administrator, you have configured a dual-rate, dual- bucket policer in accordance with RFC 2698 on the serial interface of you router, connecting to your provider. The SLA with your provider states that you should only send AF31 (limited to 150 kb/s), AF32 (limited to 50 kb/s)and AF33 (best effort). Your service provider claims you are not conforming to the SLA Which two things are wrong with this configuration? (Choose two.)
class-map match-all af31 match dscp af31 class-map match-all af32 match dscp af32 class-map match-all af33 match dscp af33 policy-map marking class af31 set dscp af31 class af32 set dscp af32 class af33 set dscp af33 policy-map limit class af33 police cir 150000 bc 50000 pir 200000 be 50000 conform-action set-dscp-transmit af31 exceed-action set-dscp-transmit af32 violate-action set-dscp-transmit default class class-default bandwidth 300 interface Ethernet0/1 ip address 3.3.3.1 255.255.255.0 no ip proxy-arp load-interval 30 half-duplex no keepalive no cdp enable service-policy input marking interface serial0/0 ip address 4.4.4.1 255.255.255.252 ip load-sharing per-packet encapsulation ppp load-interval 30 no dce-terminal-timing-enable service-policy output limit
A. The configuration of a service policy on half-duplex Ethernet interfaces is not supported.
B. The class class-default sub-command of the policy-map limit command should be set to the DSCP default.
C. The violate action is wrong.
D. This policer configuration is not implementing RFC 2698 dual-bucket, dual-rate.
E. The policer is configured in the wrong class
B. The class class-default sub-command of the policy-map limit command should be set to the DSCP default.
C. The violate action is wrong.
D. This policer configuration is not implementing RFC 2698 dual-bucket, dual-rate.
E. The policer is configured in the wrong class
Answer: C E
Question 5
Refer to the exhibit. You have noticed that several users in the network are consuming a great deal of bandwidth for the peer-to-peer application Kazaa2. You would like to limit this traffic, and at the same time provide a guaranteed 100 kb/s bandwidth for one of your servers. After applying the configuration in the exhibit, you notice no change in the bandwidth utilization on the serial link; it is still heavily oversubscribing the interface.
What is the cause of this problem?
What is the cause of this problem?
no ip cef class-map match-all kazza2 match protocol kazza2 class-map match-all server match access-group 105 policy-map p2p class kazaa2 drop class server bandwidth 100 class class-default fair-queue interface Serial0/0 bandwidth 1234 ip address 20.1.34.1 255.255.255.252 ip load-sharing per-packet encapsulation ppp load-interval 30 no dce-terminal-timing-enable service-policy output p2p
A. CEF needs to be enabled for NBAR.
B. In class Kazaa2, you should configure a policer instead of a drop command.
C. The server class should have a priority of 100.
D. The bandwidth parameter on serial 0/0 is wrong.
E. Kazaa2 is not a valid protocol.
B. In class Kazaa2, you should configure a policer instead of a drop command.
C. The server class should have a priority of 100.
D. The bandwidth parameter on serial 0/0 is wrong.
E. Kazaa2 is not a valid protocol.
Answer: A
Question 6
All of these are fundamental building blocks of a differentiated senvices Traffic Conditioner Block except which one?
A. dropper
B. classifier
C. marker
D. querier
E. meter
F. shaper
A. dropper
B. classifier
C. marker
D. querier
E. meter
F. shaper
Answer: D
Question 7
Refer to the exhibit. You would like to guarantee 7 Mb/s for FTP traffic in your LAN, as it seems that peer-to-peer traffic is taking up a large amount of bandwidth. When testing the configuration, you notice that FTP traffic doesn’t reach 7 Mb/s. What is the problem?
ip cef class-map match-all ftp match protocol ftp class-map match-all voice match precedence 5 policy-map mark class voice priority 200 class ftp set dscp af32 bandwidth 7000 random-detect dscp-based class class-default interface Tunnel1 ip address 20.1.1.1 255.255.255.252 load-interval 30 qos pre-classify tunnel source 4.4.4.1 tunnel destination 4.4.4.2 ! interface Tunnel2 ip address 20.2.2.1 255.255.255.252 load-interval 30 qos pre-classify tunnel source 4.4.4.1 tunnel destination 4.4.4.2 interface Ethernet0/1 ip address 4.4.4.1 255.255.255.0 no ip proxy-arp load-interval 30 half-duplex no keepalive no cdp enable service-policy output mark
A. The Ethernet interface should have keepalives enabled.
B. The duplex settings are wrong on the Ethernet interface.
C. The qos pre-classify command should be removed from the tunnel interfaces.
D. the priority queue for the voice class is probably taking all the bandwidth
E. there are probably not enough interface buffers; they should be tuned.
B. The duplex settings are wrong on the Ethernet interface.
C. The qos pre-classify command should be removed from the tunnel interfaces.
D. the priority queue for the voice class is probably taking all the bandwidth
E. there are probably not enough interface buffers; they should be tuned.
Answer: B
Question 8
NBAR supports all of these with the exception of which one?
A. HTTP
B. IP multicast
C. TCP flows with dynamically assigned port numbers
D. non-UDP protocols
B. IP multicast
C. TCP flows with dynamically assigned port numbers
D. non-UDP protocols
Answer: B
Explanation
NBAR classifies packets that are normally difficult to classify. For instance, some applications use dynamic port numbers. NBAR can look past the UDP and TCP header, and refer to the host name, URL, or MIME type in HTTP requests.
Question 9
Modified deficit round robin supports which of these functionalities?
A. priority queue
B. weighted fair queues
C. round-robin service of output queues
D. LLQ
B. weighted fair queues
C. round-robin service of output queues
D. LLQ
Answer: A C
Question 10
A router is connected to an HDLC circuit via a T1 physical interface. The SLA for this link only allows for a sustained rate of 768 kb/s. Bursts are allowed for up to 30 seconds at up to line rate, with a window Tc of 125 ms.
What should the Be and Be setting be when using generic traffic shaping?
A. Be = 46320000 , Bc = 96000
B. Be = 768000 Bc = 32000
C. Be = 128000 Bc = 7680
D. Be = 0 Bc = 96000
B. Be = 768000 Bc = 32000
C. Be = 128000 Bc = 7680
D. Be = 0 Bc = 96000
Answer: A
Explanation
(Notice that the sustained rate is the CIR = 768kb/s)
From the formula Tc=Bc/CIR => Bc = Tc * CIR = 125ms * 768kb/s = 96000 bits
(In fact you should calculate with the default units, that is 0.125s * 768000b/s)
The T1 speed is 1.544 Mbps = 1544000bps. “Bursts are allowed for up to 30 seconds at up to line rate” ->Be = 1544000bps * 30 = 46320000 bits.
(In fact you should calculate with the default units, that is 0.125s * 768000b/s)
The T1 speed is 1.544 Mbps = 1544000bps. “Bursts are allowed for up to 30 seconds at up to line rate” ->Be = 1544000bps * 30 = 46320000 bits.
Terminologies: The term CIR refers to the traffic rate for a VC based on a business contract.
Tc is a static time interval, set by the shaper.
Committed burst (Bc) is the number of bits that can be sent in each Tc.
Be is the excess burst size, in bits. This is the number of bits beyond Bc that can be sent after a period of inactivity.
Tc is a static time interval, set by the shaper.
Committed burst (Bc) is the number of bits that can be sent in each Tc.
Be is the excess burst size, in bits. This is the number of bits beyond Bc that can be sent after a period of inactivity.
Question 11
Which two of these parameters are used to determine a forwarding equivalence class? (Choose two)
A. IP prefix
B. Layer 2 circuit
C. RSVP request from CE for bandwidth reservation
D. BGP MED value
B. Layer 2 circuit
C. RSVP request from CE for bandwidth reservation
D. BGP MED value
Answer: A B
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