| Exam 400-101 | Question id=1296 | Infrastructure Services |
You issue the show running-config command on RouterA and receive the following partial output:
class-map voip
match ip dscp ef
class-map video
match ip dscp 41
class-map ftp
match protocol ftp
policy-map kyiv
class voip
priority percent 20
class video
bandwidth percent 40
class ftp
bandwidth remaining-percent 50
class class-default
bandwidth remaining-percent 25
!
interface FastEthernet0/1
ip address 10.20.30.1 255.255.255.0
max-reserved-bandwidth 100
service-policy output kyiv
Ho much web traffic can RouterA send out the FastEthernet0/1 interface during periods of heavy voice and video traffic?
| A. |
10Mbps | |
| B. |
15Mbps | |
| C. |
20Mbps | |
| D. |
25Mbps | |
| E. |
40Mbps |
RouterA can send 10 Mbps of web traffic out the FastEthernet0/1 interface during periods of heavy voice and video traffic. To create a Quality of Service (QoS) policy, you must perform the following steps:
1. Define one or more class maps by issuing the class-map name command.
2. Define the traffic that matches the class-map by issuing one or more match commands.
3. Define one or more policy maps by issuing the policy-map name command.
4. Link the class maps to the policy maps by issuing the class name command.
5. Define one or more actions that should be taken for that traffic class.
6. Link the policy map to an interface by issuing the service-policy {input | output} name command.
Bandwidth guarantees are set in policy-map class configuration mode. You can specify the bandwidth as a rate or as a percentage with the bandwidth and priority commands. The syntax of the priority command is priority {bandwidth | percent percentage} [burst], where bandwidth is specified in Kbps and burst is specified in bytes. The priority command creates a strict priority queue where packets are dequeued before packets from other queues are dequeued. The strict priority queue is given priority over all other traffic.
If no priority traffic is being sent, the other traffic classes can share the remaining bandwidth based on their configured values.
The bandwidth command specifies a guaranteed amount of bandwidth for a particular traffic class. The syntax of the bandwidth command is bandwidth {kbps | remaining percent percentage | percent percentage}, where kbps is the amount of bandwidth that is guaranteed to a particular traffic class.
In this scenario, Voice over IP (VoIP) traffic is given a guaranteed 20 percent of the interface's bandwidth. Video traffic is given a guaranteed 40 percent of the interface's bandwidth. Voice and video traffic can exceed these bandwidth percentages if any unused bandwidth remains.
The remaining 40 percent, or 40 Mbps, of the interface's bandwidth can be used by other traffic. If traffic does not match any traffic class, it will become part of the class-default class. In this scenario, web traffic belongs to the class-default class. Therefore, web traffic can consume 25 percent of the remaining bandwidth. If no other traffic is being sent on the interface, web traffic can consume 25 percent of the interface's bandwidth. However, when voice and video traffic are heavy, web traffic can consume 25 percent of the remaining 40 Mbps, which is equal to 10 Mbps.
Even less web traffic can be sent if File Transfer Protocol (FTP) traffic or other unclassified traffic is heavy. FTP traffic can consume 50 percent of the remaining bandwidth on the interface. If no other traffic is being sent on the interface, FTP traffic can consume 50 percent of the interface's bandwidth. During periods of heavy voice and video usage, FTP traffic can consume 50 percent of the remaining 40 Mbps, which is equal to 20 Mbps.