Modular QoS Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Release

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Modular QoS Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Release

QoS on BVI

Updated: June 9, 2026

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Explains how QoS policies operate on bridged virtual interfaces in a two-pass forwarding model and identifies the release-specific capabilities available for Layer 2-to-Layer 3 and Layer 3-to-Layer 2 traffic flows.

QoS on Bridged Virtual Interfaces (BVIs) is a two-pass QoS processing model that

  • applies independent QoS processing during Layer 2 and Layer 3 forwarding,

  • enables traffic classification and marking as packets transition between bridge domains and routed interfaces, and

  • provides consistent QoS treatment across Layer 2 and Layer 3 forwarding boundaries.

In a two-pass BVI forwarding model, the router separates the Layer 2 and Layer 3 forwarding chains. This separation lets the router apply QoS policies at the appropriate logical interface in each forwarding pass.

Table 1. Feature History Table

Feature Name

Release Information

Feature Description

QoS on bridged virtual interfaces

Release 26.2.1

Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100] (select variants only*); Modular Systems (8800 [LC ASIC: P100]) (select variants only*)

You can now apply ingress policing and egress QoS policies on BVI interfaces. The feature extends QoS processing beyond ingress classification and marking and preserves QoS metadata across BVI recycle operations for consistent traffic treatment throughout the forwarding pipeline.

*This feature is supported on:

  • 8212-48FH-M

  • 8711-32FH-M

  • 88-LC1-12T24F-E

  • 88-LC1-52Y8H-EM

  • 88-LC1-36EH

Bridged virtual interface two-pass QoS

Release 25.4.1

Introduced in this release on: Fixed Systems (8200 Series [ASIC: P100], 8700 Series [ASIC: P100]) (select variants only*)

You can now apply consistent QoS treatment for traffic that moves from a bridge domain to a routed BVI. The router performs two independent ingress QoS processing passes: it first classifies and marks traffic using Layer 2 attributes inside the bridge domain, and then applies a second Layer 3-based classification at the BVI ingress. This helps with accurate class assignment and predictable queuing for bridged-to-routed flows.

*This feature is supported on:

  • 8212-48FH-M

  • 8711-32FH-M

Benefits of QoS on bridged virtual interfaces

QoS on bridged virtual interfaces helps you apply predictable QoS treatment when traffic crosses Layer 2 and Layer 3 forwarding boundaries.

QoS on BVIs provides these benefits:

  • Independent Layer 2 and Layer 3 QoS processing: You can apply separate ingress QoS processing at the Layer 2 bridge domain and at the Layer 3 BVI boundary. This ensures that packets are evaluated using the appropriate header fields at each stage of the forwarding path.

  • Consistent traffic treatment across forwarding domains: The router evaluates traffic during the appropriate forwarding pass, which helps maintain predictable QoS behavior as traffic transitions between bridging and routing.

    The router performs classification twice: once using Layer 2 attributes, and then using Layer 3 attributes. This preserves accurate class assignment for bridged-to-routed flows and allows Layer 3 QoS policies to work predictably.

  • Improved policy design flexibility: You can design policies that use Layer 2 attributes, Layer 3 attributes, or both, depending on where the traffic is processed. You are not constrained by a single-pass QoS model. This flexibility is especially useful in multi-tenant or service-edge deployments.

  • Ingress policing on BVI interfaces: From IOS XR Release 26.2.1, you can enforce traffic rates at the BVI ingress by applying policers in ingress QoS policies.

  • Egress QoS treatment on BVI interfaces: From IOS XR Release 26.2.1, you can classify and mark traffic in the egress direction of the BVI forwarding path.

  • QoS metadata preservation: From IOS XR Release 26.2.1, qos-group, traffic-class, and discard-class values can be preserved across BVI forwarding and used by later QoS policies.

How QoS on bridged virtual interfaces works

In two-pass BVI forwarding, the router separates Layer 2 and Layer 3 forwarding. The packet is processed once in the first forwarding domain and again when it transitions through the BVI into the next forwarding domain.

From IOS XR Release 26.2.1, the BVI QoS model supports a broader set of QoS actions for both Layer 2-to-Layer 3 and Layer 3-to-Layer 2 traffic flows.

Summary

The BVI QoS model uses these components:

  • Layer 2 interface: Receives or forwards traffic within the bridge domain.

  • Layer 3 interface: Receives or forwards routed traffic.

  • BVI: Acts as the logical boundary between Layer 2 and Layer 3 forwarding and applies QoS policies in the applicable direction.

  • Recycle path: Carries packet metadata between forwarding passes so that QoS information can be reused by subsequent policies.

  • Egress physical or bundle port: Forwards the routed packet out of the router.

Workflow

These stages describe how the router processes traffic through the BVI QoS model.

  1. Traffic moves from Layer 2 to Layer 3.
    • The packet enters a Layer 2 interface that belongs to a bridge domain.
    • The router performs the first forwarding pass in the Layer 2 domain.
    • The packet is recycled for the second pass forwarding and then passes through the BVI interface.
    • The router applies BVI ingress QoS processing during the Layer 3 forwarding pass.
    • From IOS XR Release 26.2.1, the BVI ingress policy can classify, mark, and police traffic in this forwarding path.
  2. Traffic moves from Layer 3 to Layer 2.
    • The packet enters a Layer 3 interface and is routed toward a bridge domain through the BVI.
    • The router performs the first forwarding pass in the Layer 3 domain.
    • The packet transitions through the BVI and is recycled for the Layer 2 forwarding pass.
    • From IOS XR Release 26.2.1, the BVI egress policy can classify and mark traffic in this forwarding path.
    • The packet exits through the Layer 2 interface in the bridge domain.
  3. The router preserves QoS metadata across BVI forwarding.
    • From IOS XR Release 26.2.1, qos-group values can be carried across the BVI recycle path and used by later QoS policies.
    • From IOS XR Release 26.2.1, traffic-class and discard-class values can be preserved across BVI forwarding and can be overwritten by a marking policy applied on the BVI.

Usage guidelines for QoS on bridged virtual interfaces

Use absolute rates for BVI ingress policers

From IOS XR Release 26.2.1, configure BVI ingress policers with absolute bandwidth values.

BVI policers are programmed at the slice level. The configured policer rate is distributed across the slices that participate in forwarding for the BVI.

BVI policers are programmed at the slice level. The user-configured policer rate is distributed across the slices within an NPU. The policer rate per slice is calculated as the configured policer rate divided by the number of slices in the NPU.

Use preserved QoS metadata for downstream policies

From IOS XR Release 26.2.1, use preserved qos-group, traffic-class, and discard-class values to maintain consistent QoS treatment across BVI forwarding.

Preserving QoS metadata across the recycle path lets a downstream policy classify or mark traffic based on QoS values set in an earlier forwarding pass.

Limitations for QoS on bridged virtual interfaces

Limitations in releases earlier than IOS XR Release 26.2.1

  • QoS on BVI is limited to ingress classification and ingress marking.

  • Ingress classification on BVI interfaces supports ACL, DSCP, and precedence match criteria only.

  • Ingress marking on BVI interfaces supports traffic-class and MPLS EXP marking actions only.

  • Ingress policing, egress classification, and egress marking are not supported on BVI interfaces.

Classification limitations from IOS XR Release 26.2.1

  • Qos-group-based classification is not supported in ingress BVI QoS policies.

  • ACL-based classification is not supported in egress BVI QoS policies.

Marking limitations from IOS XR Release 26.2.1

  • Qos-group marking is not supported in BVI egress QoS policies.

  • If a BVI marking policy sets only traffic-class and does not set discard-class, the discard-class value is reset to 0.

  • If a BVI marking policy sets only discard-class and does not set traffic-class, the traffic-class value is reset to 0.

Policing and queuing limitations from IOS XR Release 26.2.1

  • Policing is not supported in BVI egress QoS policies.

  • Policing is supported in BVI ingress QoS policies only with absolute units.

  • Policers with multicast traffic over a BVI interface can reach a maximum rate up to the per-slice bandwidth programmed on an NPU.

  • Queueing policy maps are not supported on BVI interfaces.

Configure BVI two-pass QoS for ingress classification and marking

Apply an ingress QoS policy to a BVI interface to classify and mark traffic that moves from a bridge domain to a routed BVI.

This procedure preserves the earlier release scope of BVI two-pass QoS. For the expanded QoS capability introduced from IOS XR Release 26.2.1, use the procedure to configure QoS policies on bridged virtual interfaces.

Procedure

1.

Define class maps to match DSCP values.

Example:

Router#configure
Router(config)#class-map match-all DSCPAF23_TABLE
Router(config-cmap)#match dscp af23
Router(config-cmap)#end-class-map
Router(config)#class-map match-all DSCPAF41_TABLE
Router(config-cmap)#match dscp af41
Router(config-cmap)#end-class-map
2.

Create an ingress policy map and assign marking actions.

Example:

Router(config)#policy-map BVI_INGRESS_MARK
Router(config-pmap)#class DSCPAF23_TABLE
Router(config-pmap-c)#set traffic-class 2
Router(config-pmap-c)#set mpls experimental imposition 2
Router(config-pmap-c)#exit
Router(config-pmap)#class DSCPAF41_TABLE
Router(config-pmap-c)#set traffic-class 5
Router(config-pmap-c)#set mpls experimental imposition 5
Router(config-pmap-c)#exit
Router(config-pmap)#end-policy-map
3.

Attach the policy map to the BVI interface in the input direction.

Example:

Router(config)#interface bvi 1
Router(config-if)#service-policy input BVI_INGRESS_MARK
Router(config-if)#commit
4.

Verify the QoS policy applied to the BVI interface.

Example:

Router#show qos interface bvi 1 input
Router#show policy-map interface bvi 1 input

Configure QoS policies on bridged virtual interfaces

Procedure

1.

Create class maps for BVI ingress classification.

From Cisco IOS XR Release 26.2.1, use ingress BVI class maps to classify traffic by DSCP, precedence, or ACL match criteria.

Example:

Router#configure
Router(config)#class-map match-all BVI_IN_DSCP_AF23
Router(config-cmap)#match dscp af23
Router(config-cmap)#end-class-map
Router(config)#class-map match-all BVI_IN_DSCP_AF41
Router(config-cmap)#match dscp af41
Router(config-cmap)#end-class-map
2.

Create a BVI ingress policy map with marking and policing actions.

From Cisco IOS XR Release 26.2.1, you can configure BVI ingress marking actions and apply ingress policers with absolute rate values.

Example:

Router(config)#policy-map BVI_INGRESS_QOS
Router(config-pmap)#class BVI_IN_DSCP_AF23
Router(config-pmap-c)#set traffic-class 2
Router(config-pmap-c)#set discard-class 1
Router(config-pmap-c)#set qos-group 2
Router(config-pmap-c)#police rate 100 mbps peak-rate 200 mbps
Router(config-pmap-c)#exit
Router(config-pmap)#class BVI_IN_DSCP_AF41
Router(config-pmap-c)#set traffic-class 5
Router(config-pmap-c)#set discard-class 0
Router(config-pmap-c)#set qos-group 5
Router(config-pmap-c)#exit
Router(config-pmap)#end-policy-map
3.

Attach the BVI ingress policy map to the BVI interface.

Example:

Router(config)#interface bvi 1
Router(config-if)#service-policy input BVI_INGRESS_QOS
Router(config-if)#commit
4.

Create class maps for BVI egress classification.

From Cisco IOS XR Release 26.2.1, use egress BVI class maps to classify traffic by DSCP, precedence, or qos-group values.

Example:

Router(config)#class-map match-all BVI_EG_QG2
Router(config-cmap)#match qos-group 2
Router(config-cmap)#end-class-map
Router(config)#class-map match-all BVI_EG_QG5
Router(config-cmap)#match qos-group 5
Router(config-cmap)#end-class-map
5.

Create a BVI egress policy map with marking actions.

From Cisco IOS XR Release 26.2.1, use BVI egress marking to update DSCP, precedence, traffic-class, or discard-class values.

Example:

Router(config)#policy-map BVI_EGRESS_MARK
Router(config-pmap)#class BVI_EG_QG2
Router(config-pmap-c)#set dscp af23
Router(config-pmap-c)#set traffic-class 2
Router(config-pmap-c)#set discard-class 1
Router(config-pmap-c)#exit
Router(config-pmap)#class BVI_EG_QG5
Router(config-pmap-c)#set dscp af41
Router(config-pmap-c)#set traffic-class 5
Router(config-pmap-c)#set discard-class 0
Router(config-pmap-c)#exit
Router(config-pmap)#end-policy-map
6.

Attach the BVI egress policy map to the BVI interface.

Example:

Router(config)#interface bvi 1
Router(config-if)#service-policy output BVI_EGRESS_MARK
Router(config-if)#commit
7.

Verify the BVI QoS configuration.

Example:

Router#show qos interface bvi 1 input
Router#show qos interface bvi 1 output
Router#show policy-map interface bvi 1 input
Router#show policy-map interface bvi 1 output

The BVI interface applies QoS treatment in the configured direction. Ingress policy statistics show classification, marking, and policing results. Egress policy statistics show downstream classification and marking results.