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Example: Configuring DiffServ for IPv6


The example assigns expedited forwarding to Q1 and a subset of the assured forwarding classes (af1x) to Q2, and distributes resources among all four forwarding classes.

Figure 1 shows the topology of the three routers and links that are used as a case study in this chapter.

Figure 1: Basic IPv6 DiffServ TopologyBasic IPv6 DiffServ Topology

In this case study, the service provider has agreed to provide high-priority delivery of packets for two applications between the customer’s servers at two sites. The first application generates streams of high-definition audiovisual (television) packet flows and the second generates large quantities of time-sensitive financial information. In all cases, the packet flow is from server to server. The service provider marks the packets appropriately as they enter the network from either site, configures special queues and forwarding classes for this traffic on the three routers, and uses DiffServ for IPv6 for this purpose.

Routers 1 and 3 use multifield (MF) classifiers on the customer-facing interfaces to detect high-priority packets and rewrite the Differentiated Services code points (DSCPs) appropriately. Best-effort data and network control packets are not affected. All three routers are configured with consistent schedulers and resources to handle high-priority packets properly.

Figure 2: IPv6 DiffServ ConfigurationIPv6 DiffServ Configuration

Figure 2 shows the complete topology for IPv6 DiffServ, complete with interfaces and IPv6 addresses. The IPv4-mapped IPv6 address format described in RFC 5952 is used.

Begin your configuration on Router 2, the core router. This ensures that when DiffServ is enabled on the edge routers, class of service (CoS) is enabled end to end through the network. The core router configuration is a little simpler because no MF classification is configured in the core.

Router 2

Continue your configuration on Router 1 and Router 3, the edge routers. These routers get firewall-filter-based MF classifiers and rewrite rules for markers as well as schedulers and drop profiles on the core-facing interfaces.

Router 1

Router 3


To verify that your CoS using IPv6 DiffServ configuration is correct, use the following commands:

  • show class-of-service classifier type dscp-ipv6

  • show class-of-service rewrite-rule type dscp-ipv6

  • show class-of-service interface

  • show class-of-service forwarding-table classifier mapping

  • show class-of-service forwarding-table rewrite-rule mapping

  • show class-of-service scheduler-map scheduler-map-name

  • show class-of-service forwarding-table scheduler-map

The following section shows the output of these commands used with the configuration example.

DiffServ Classifiers

Rewrite Rules

Class-of-Service Interfaces

Classifier Mapping

Rewrite Rule Mapping

Scheduler Map