Method and apparatus for learning and switching frames in a distributed network switch

US6807172B1 · kind B1 · utility

Assignee

• Cisco Technology, Inc. · US

Inventors

• Herman Levenson · Palo Alto, US
• Jonathan Davar · Los Altos Hills, US
• Ajit Sanzgiri · Los Gatos, US
• Thomas J. Edsall · Los Gatos, US
• Chingwei Chang · Vancouver, US
• Rong-Lung Lue · Saratoga, US
• Saravanakumar Rajendran · San Jose, US
• Tuan Thanh Nguyen · Milpitas, US
• Claudette Lucille Surma · Fremont, US

Key dates

• Filing date: Dec 21, 1999
• Grant date: Oct 19, 2004
• Expiry date: Dec 21, 2019

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04L49/40
• WIPO field: Digital communication
• WIPO sector: Electrical engineering

Abstract

A technique enables learning and switching of frames between line cards that are interconnected by a switch fabric of a distributed network switch. The network switch comprises a router and a plurality of forwarding engines, each having an associated forwarding table. The distributed learning and switching technique configures (i) the router to issue an extra copy of a routed frame to an ingress card having a port attached to the source of the frame; (ii) the router to ensure that the contents of a source index field of the routed frame header indicate that the frame originated from the ingress card; (iii) the router to assert a shortcut bit in the header of the routed frame; (iv) a forwarding engine on an egress card having a port attached to the destination of the frame to generate and issue a media access control notification frame to the ingress card and (v) a forwarding engine on the ingress card to mark an established entry in a layer 2 (L2) portion of its forwarding table as ineligible for normal L2 aging policies.