Mapping C-Tag to S-Tag dot1p ValuesTo map C-Tag dot1p values to S-Tag dot1p values and mark the frames accordingly, use the followingcommands.1. Allocate CAM space to enable queuing frames according to the C-Tag or the S-Tag.CONFIGURATION modecam-acl l2acl number ipv4acl number ipv6acl number ipv4qos number l2qosnumber l2pt number ipmacacl number ecfmacl number {vman-qos | vman-qos-dual-fp} number• vman-qos: mark the S-Tag dot1p and queue the frame according to the original C-Tag dot1p.This method requires half as many CAM entries as vman-qos-dual-fp.• vman-qos-dual-fp: mark the S-Tag dot1p and queue the frame according to the S-Tag dot1p.This method requires twice as many CAM entries as vman-qos and FP blocks in multiples of 2.The default is: 0 FP blocks for vman-qos and vman-qos-dual-fp.2. The new CAM configuration is stored in NVRAM and takes effect only after a save and reload.EXEC Privilege modecopy running-config startup-config3. Reload the system.reload4. Map C-Tag dot1p values to a S-Tag dot1p value.INTERFACE modevlan-stack dot1p-mapping c-tag-dot1p values sp-tag-dot1p valueSeparate C-Tag values by commas. Dashed ranges are permitted.Dynamic Mode CoS overrides any Layer 2 QoS configuration in case of conflicts.NOTE: Because dot1p-mapping marks and queues packets, the only remaining applicable QoSconfiguration is rate metering. You may use Rate Shaping or Rate Policing.Layer 2 Protocol TunnelingSpanning tree bridge protocol data units (BPDUs) use a reserved destination MAC address called thebridge group address, which is 01-80-C2-00-00-00.Only spanning-tree bridges on the local area network (LAN) recognize this address and process theBPDU. When you use VLAN stacking to connect physically separate regions of a network, BPDUsattempting to traverse the intermediate network might be consumed and later dropped because theintermediate network itself might be using spanning tree (shown in the following illustration).824 Service Provider Bridging
