21-2
Cisco 10000 Series Router Quality of Service Configuration Guide
OL-7433-09
Chapter 21 VLAN Tag-Based Quality of Service
VLAN Tag-Based QoS
For hierarchical QoS policies, the router applies the parent shape rate to each group of VLANs. At most,
a single VLAN can have a throughput equal to the parent shape rate. If all of the VLANs within the
VLAN group are active, the aggregate traffic of all active VLAN-group members is limited to the shape
rate.
In an 802.1Q VLAN implementation, the router passes a packet to the dot1q-encapsulated subinterface
only if the VLAN ID of the packet matches the VLAN ID configured for the subinterface. Otherwise,
the router passes the packet to the main interface. Therefore, you must create a subinterface with a
specific VLAN ID before the router can apply QoS on a VLAN ID that is configured as part of a VLAN
group.
Feature History for VLAN Tag-Based QoS
VLAN-Groups
A VLAN-group is a traffic class that potentially consists of multiple IEEE 802.1Q VLAN subinterfaces.
A class map defines the VLAN group and the match criteria the router uses to classify the traffic as
belonging to a specific VLAN group. All of the subinterfaces belonging to a VLAN group share the
bandwidth allocated to the group and share the same class queue.
The
match vlan
command allows you to specify the VLANs you want to include in a VLAN group. The
configuration of a VLAN group can include individual VLAN ID values or a range of values. For
example, VLANs with IDs 3, 5-8, and 10 can form a VLAN group. The router treats the VLANs
specified in a VLAN group as an aggregate whole.
Note
If you specify the
match vlan
command in a class map, you cannot specify other
match
commands in
the same class map. Use the
match vlan
command only for VLAN grouping.
Only Ethernet, Fast Ethernet, and Gigabit Ethernet interfaces support VLAN groups. For outbound
VLAN tag-based policies, use a
shape
command for each VLAN group.
VLAN-Group Policy Map
A VLAN-group policy map defines QoS services for traffic classes that consists of multiple IEEE
802.1Q VLAN subinterfaces (see the
“VLAN-Groups” section on page 21-2
). In this way, you can apply
a single QoS policy to multiple VLANs belonging to specific VLAN-group classes.
You can attach a VLAN-group policy map to only the main interface. The subinterfaces on the main
interface inherit the service policy.
The amount of policy space used is equivalent to the number of VLAN groups defined in the policy,
including the VLAN groups defined in match-VLAN class maps and in the class-default class. The limit
of available policy space is equivalent to 4096 policy maps.
Cisco IOS Release
Description
Required PRE
Release 12.2(31)SB22
This feature was introduced and implemented on the
Cisco 10000 series router for the PRE2 and PRE3.
PRE2
PRE3
