monitoring process. Cisco AutoQoS provides
visibility into the classes of service deployed via system
logging and Simple Network Management Protocol (SNMP) traps,
with notification of abnormal events (for example, VoIP packet
drops). Once AutoQoS is turned on, SNMP traps generated by
Cisco AutoQoS are delivered only if an SNMP server is
explicitly enabled and the community string "AutoQoS"
is given write permission. In the case of low-speed Frame
Relay/ATM and serial links, Cisco AutoQoS must be enabled on
both ends of the connection to function correctly. Also,
because the fragmentation parameters are derived from the
bandwidth, the bandwidth parameter on both ends of the link
must be identical. The show auto qos output displays the
information that Remote Monitoring (RMON) traps logging voice
packet drops is enabled. This output is used for monitoring and
troubleshooting. AutoQoS activates thresholds in the RMON alarm
table to monitor drops in LLQ. By default, the drop threshold
is set to 1 bps. Figure shows an example of an alarm event
triggered by dropped packets. In some situations, as shown in
the output for Frame Relay, Cisco AutoQoS also projects new
traffic parameters. In Figure , Cisco AutoQoS generated the new
Frame Relay map class, which is mapped to the specific DLCI
using the invented map class name. Finally, the show auto
qos output displays how the QoS policy was applied in the
configuration. In this case, the service policy was applied to
the new Frame Relay map class, which in turn was mapped to the
DLCI. In addition to the contents of the interface
configurations, you can also display policy maps and class maps
using the show auto qos command. Access control lists
(ACLs) are also displayed if Cisco AutoQoS generated them.
Content 5.2 Mitigating Common
Cisco AutoQoS Issues 5.2.6 Modifying the Active
Cisco AutoQoS Configuration with MQC If the policy maps and
class maps created based on the templates generated by Cisco
AutoQoS for the Enterprise do not meet the needs of the
enterprise network, use the appropriate Cisco IOS commands to
make the necessary changes. This issue usually occurs in two
situations: - The new Cisco AutoQoS generated
configuration does not meet specific enterprise
expectations.
- Network or traffic conditions have
changed while Cisco AutoQoS generated the configuration, and
network administrators have the necessary skills to adapt the
existing QoS configuration rather than running the entire Cisco
AutoQoS deployment procedure again.
Figure provides
a decision map to assist you in deciding whether you need to
make manual modifications. Caution
Although you can
modify the policy maps and class maps, they may not be removed
properly when Cisco AutoQoS for the Enterprise is disabled
using the no auto qos command. You may have to remove
any modified policy maps and class maps manually. Modifying
the Active Cisco AutoQoS Configuration with MQC:
Classification
Most commonly, Cisco AutoQoS uses NBAR
and ACLs for traffic classification. However, any Cisco MQC
classification mechanism can supplement or replace the
configuration generated by Cisco AutoQoS. Significant skills
and MQC knowledge are required to perform the modification, but
this procedure can adapt the classification to even the most
complex classification rules. Classification can be modified
either after the Cisco AutoQoS discovery but before the
generated policy templates are applied or after the policy
templates generated by Cisco AutoQoS are applied. There are
several ways to tune and modify the existing class maps:
- Directly at the router command-line interface (CLI) using
MQC
- Using Cisco QoS Policy Manager (QPM)
However, the easiest way to tune the existing class maps is to
copy them into a text editor and modify the configuration
offline. Add the desired new classification and remove the
undesired existing classification. When the modification is
complete, copy the new classification from the editor and paste
it to a router configuration prompt to push the rules through
the built-in parser of the router. Figure summarizes these
points with an example. If required, you can repeat the tuning
procedure in an iterative process until you achieve the optimal
configuration. Cisco MQC offers a broad range of classification
options, to use when adding to the class map rules generated by
Cisco AutoQoS. Figure summarizes these points and the table
lists the most common classification options and their
respective match commands. Besides these classification
options, any classification supported by Cisco MQC can be used
in any combination to meet specific classification
requirements. Example: Classification Tuning Using the
MQC
The following is an example of classification
tuning using the MQC: - Start the Cisco AutoQoS
discovery process.
Router#configure terminal
Router(config)#interface serial0/1/0
Router(config-if)#bandwidth 384
Router(config-if)#auto discovery qos
Router(config-if)#end
- Leave the Cisco
AutoQoS discovery running for several days.
-
Review the Cisco AutoQoS discovery results and identify
classification changes required (only the classification
portion is shown).
Router#show auto discovery
qos
<output omitted>
!
Suggested AutoQoS
Policy for the current uptime:
class-map match-any
AutoQoS-Voice-Se0/1/0
match protocol rtp audio
!
class-map match-any AutoQoS-Signaling-Se0/1/0
match
protocol h323
!
class-map match-any
AutoQoS-Transactional-Se0/1/0
match protocol sqlnet
match protocol citrix
!
class-map match-any
AutoQoS-Bulk-Se0/1/0
match protocol exchange
match
protocol ftp
!
class-map match-any
AutoQoS-Scavenger-Se0/1/0
match protocol kazaa2
!
class-map match-any AutoQoS-Management-Se0/1/0
match
protocol ldap Necessary classification changes include these:
Step 1 Also, classify Session Initiation Protocol (SIP)
and Media Gateway Control Protocol (MGCP) signaling. Step
2 Classify Telnet traffic as Transactional class. Step
3 Move the SQL classification from the Transactional class
to the Bulk class. Step 4 Classify all SNMP traffic
coming from the IP subnet 193.87.95.0 as Management class.
- Apply the generated Cisco AutoQoS policy
template to the interface for later modification.
Router#configure terminal
Router(config)#interface serial0/1/0
Router(config-if)#auto qos
Router(config-if)#end
- Modify the
classification generated by Cisco AutoQoS according to the
requirements.
Step 1 Also, classify SIP and MGCP
signaling.
Router#configure terminal
Router(config)#class-map AutoQoS-Signaling-Se0/1/0
Router(config-cmap)#match protocol sip
Router(config-cmap)#match protocol mgcp
Router(config-cmap)#exit Step 2 Classify Telnet
traffic as Transactional.
Router(config)#class-map
AutoQoS-Transactional-Se0/1/0
Router(config-cmap)#match protocol telnet
Router(config-cmap)#exit Step 3 Move the SQL
classification from the Transactional class to the Bulk
class.
Router(config)#class-map
AutoQoS-Transactional-Se0/1/0
Router(config-cmap)#no
match protocol sqlnet
Router(config-cmap)#exit