Cisco Technology, Inc.

Cisco Systems Inc.

Soei-Shin Hang

Thomas James Edsall

Luca Cafiero

Karl S Nakamura

Maurilio Tazio De Nicolo

Silvano Gai

Sanjay Sane

Elango Ganesan

Ramana Mellacheruvu

Lawrence Rolfe Kreeger

Daniel R Ullum

Daniel Ullum

A solution is provided wherein the interfaces between multiple chassis (e.g., edge switches) in a network of layer 2 devices and a spanning tree device are treated as a single emulated switch. This emulated switch effectively enables two different views to the two different sides. Thus, frames from the network of layer 2 switches destined to any port of the emulated switch may take any of the links (through any of the physical switches), thereby enabling effective load-balancing for frames traveling from the layer 2 network side into the spanning tree device. Meanwhile the spanning tree device does not recognize an illegal loop in its connection to two different edge switches as it views the two links as a single logical EtherChannel.

Multi-chassis emulated switch

A network node determines the suitability of coupled devices for being remotely line powered before actually powering them. The node scan its ports to determine which ports are coupled to devices. The node then interrogates the coupled devices. A unique discovery tone or bit pattern is generated and sent to devices coupled to ports. The node then monitors the port for a return signal. If there is a return signal, it is compared to the transmitted discovery signal. The signal will be identical after allowing for line losses if the coupled device is suitable for remote line powering. If the comparison yields a match, the network node supplies remote line power to the device.

Method and apparatus for remote powering of device connected to network

The invention replicates a packet requiring high availability and transmits it from two or more ports of a switch, for example a wiring closet Layer 2 switch. The parent packet carries a unique sequence number. The copies of the packet each carry the parent packet's unique sequence number. Each copy of the packet then travels on separate pathways through routers (Layer 3 network devices). The pathways are maintained separate by assigning high costs in a LSP routing sense to links connecting the two paths, and by assigning low costs to links along the desired paths. The two identical packets converge on the destination station. The destination station accepts the first packet with a particular sequence number, and discards any later packets with the same sequence number. In the event that a link in one path has a catastrophic failure, then the packet travelling along the other path reaches the destination station and service remains operative without interruption. The lost path is then recomputed by the a router (if any) still receiving the lost packet. A new non-converging path may be selected if any are available, depending upon the topology. After the disruption is repaired, the original dual pathways may once again be established.

Multiple packet paths to improve reliability in an IP network

An improved look up mechanism for accessing a RAM to obtain forwarding information for data frames being transported among ports of a high-performance switch is provided. The look up mechanism includes a multi-page look up table and associated hashing technique. A media access control (MAC) address and a virtual local area network (VLAN) identifier are transformed with a hash function to obtain a hash key. The hash key is an address pointing to a particular entry in the look up table. A virtual first page is also derived from the hash key, which selects a particular physical page of the look up table to be initially accessed each time that MAC address/VLAN pair is used. The look up mechanism may also be used to access a short cut table containing Layer short cut information. In either case, ultimately, the likelihood is increased that a match will be found on the first RAM access, thus maintaining high-speed switch performance.

Network switch with hash table look up

An improved look up mechanism for accessing a RAM to obtain forwarding information for data frames being transported among ports of a high-performance switch is provided. The look up mechanism includes a multi-page look up table and associated hashing technique. A media access control (MAC) address and a virtual local area network (VLAN) identifier are transformed with a hash function to obtain a hash key. The hash key is an address pointing to a particular entry in the look up table. A virtual first page is also derived from the hash key, which selects a particular physical page of the look up table to be initially accessed each time that MAC address/VLAN pair is used. The look up mechanism may also be used to access a short cut table containing Layer 3 short cut information. In either case, ultimately, the likelihood is increased that a match will be found on the first RAM access, thus maintaining high-speed switch performance.

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Sunnyvale, CA, United States of America

Soei-Shin Hang