Systems and methods for dynamically learning virtual local area network (VLAN) tags

摘要

A system for dynamically learning virtual local area network (VLAN) tags comprises a switching element having a VLAN table and a media access control (MAC) table. For at least one VLAN, the switching element is configured to dynamically learn VLAN tags for packets carried by the VLAN in order to build the VLAN table and to then use mappings of the VLAN table, rather than mappings of the MAC table, to make forwarding decisions for all types of packets carried by the VLAN. The MAC table is not used for forwarding decisions for packets carried by the VLAN, but it can be used to help learn the VLAN tags. In particular, the switching element can use the MAC table to selectively trap packets when they are useful for learning VLAN tags and to prevent MAC learning traps for packets carrying VLAN tags previously learned by the switching element.

主权项

1. A switching element, comprising:
a plurality of ports, including at least a first port and a second port; memory for storing a media access control (MAC) table and a virtual local area network (VLAN) table, the MAC table mapping MAC addresses to port identifiers identifying the ports and the VLAN table mapping VLAN tags to port identifiers identifying the ports; forwarding logic configured to receive a plurality of data packets from the ports, wherein for at least one of the data packets the forwarding logic is configured to search the MAC table for a mapping corresponding to a destination MAC address of the one data packet and to forward the one data packet to at least the second port based on the VLAN table in response to a MAC table miss for the destination MAC address, wherein the forwarding logic is configured to trap one of the data packets received from the first port such that metadata of the trapped data packet is transmitted to an exceptions queue in response to a MAC table miss for a source MAC address of the trapped data packet; and table managing logic configured to dynamically learn a plurality of VLAN tags based on the plurality of data packets and to build the VLAN table based on the learned VLAN tags, wherein the table managing logic for each of the learned VLAN tags is configured to update, in response to one of the data packets carrying the learned VLAN tag, the VLAN table to associate the learned VLAN tag with a port identifier identifying one of the ports that received the one data packet carrying the learned VLAN tag, wherein the table managing logic is configured to update the VLAN table based on the metadata such that the VLAN table associates a VLAN tag of the trapped data packet with a port identifier identifying the first port, and wherein the table managing logic is configured to disable, in response to the metadata, the switching element from updating the MAC table to learn the VLAN tag of the trapped data packet from data packets received by the first port.