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148 Quality of Service
Example #2: Configuring DiffServ VoIP Support
Enter Global Config mode. Set queue 6 on all ports to use strict priority mode. This queue shall be used
for all VoIP packets. Activate DiffServ for the switch.
console#config
cos-queue strict 6
diffserv
Create a DiffServ classifier named class_voip and define a single match criterion to detect UDP packets.
The class type match-all indicates that all match criteria defined for the class must be satisfied in order
for a packet to be considered a match.
class-map match-all class_voip
match protocol udp
exit
Create a second DiffServ classifier named class_ef and define a single match criterion to detect a
DiffServ code point (DSCP) of EF (expedited forwarding). This handles incoming traffic that was
previously marked as expedited elsewhere in the network.
class-map match-all class_ef
match ip dscp ef
exit
Create a DiffServ policy for inbound traffic named pol_voip, then add the previously created classes
'class_ef' and 'class_voip' as instances within this policy.
This policy handles incoming packets already marked with a DSCP value of EF (per class_ef definition),
or marks UDP packets per the class_voip definition) with a DSCP value of EF. In each case, the
matching packets are assigned internally to use queue 6 of the egress port to which they are forwarded.
policy-map pol_voip in
class class_ef
assign-queue 5
exit
class class_voip
mark ip-dscp ef
assign-queue 5
exit
exit
Attach the defined policy to an inbound service interface.
interface ethernet 1/g1
service-policy in pol_voip
exit
exit