Cisco NME-16ES-1G User Guide - Page 35

16- and 36-Port Ethernet Switch Module for Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Feature Overview • On an interface configured for QoS, all traffic received through the interface is classified, policed, and marked according to the policy map attached to the interface. On a trunk interface configured for QoS, traffic in all VLANs received through the interface is classified, policed, and marked according to the policy map attached to the interface. • VLAN-based egress DSCP-to-COS mapping is supported. DSCP-to-COS mapping occurs for all packets with a specific VLAN ID egressing from the CPU to the physical port. The packets can be placed in the physical port egress queue depending on the COS value. Packets are handled according to type of service. Note No policers can be configured on the egress interface on Ethernet switch network modules. Mapping Tables The Ethernet switch network modules support these types of marking to apply to the switch: • CoS value to the DSCP value • DSCP value to CoS value Note An interface can be configured to trust either CoS or DSCP, but not both at the same time. Before the traffic reaches the scheduling stage, QoS uses the configurable DSCP-to-CoS map to derive a CoS value from the internal DSCP value. The CoS-to-DSCP and DSCP-to-CoS map have default values that might or might not be appropriate for your network. For configuration information, see the "Configuring CoS Maps" section on page 96. Maximum Number of VLAN and Multicast Groups The maximum number is less than or equal to 242. The number of VLANs is determined by multiplying the number of VLANs by the number of multicast groups. For example, the maximum number for 10 VLANs and 20 groups would be 200, under the 242 limit. IP Multicast Support The maximum number of multicast groups is related to the maximum number of VLANs. The product of the number of multicast groups and the number of VLANs cannot exceed 242. This feature also provides support for Protocol Independent Multicast (PIM) sparse mode/dense mode sparse-dense mode. IGMP Snooping Understanding IGMP Snooping Internet Group Management Protocol (IGMP) snooping constrains the flooding of multicast traffic by dynamically configuring the interfaces so that multicast traffic is forwarded only to those interfaces associated with IP multicast devices. The LAN switch snoops on the IGMP traffic between the host and the router and keeps track of multicast groups and member ports. When the switch receives an IGMP join report from a host for a particular multicast group, the switch adds the host port number to the Cisco IOS Release 12.2(2)XT, 12.2(8)T, and 12.2(15)ZJ 35