Cisco MDS-9124 Troubleshooting Guide - Page 215
Troubleshooting PortChannels and Trunking, PortChannel Overview
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Send documentation comments to [email protected] 10 C H A P T E R Troubleshooting PortChannels and Trunking PortChannels refer to the aggregation of multiple physical interfaces into one logical interface to provide higher aggregated bandwidth, load balancing, and link redundancy. This chapter includes the following topics: • PortChannel Overview, page 10-1 • Initial Troubleshooting Checklist, page 10-2 • PortChannel Issues, page 10-3 • Trunking Issues, page 10-4 PortChannel Overview A PortChannel has the following functionality: • Provides a point-to-point connection over ISL (E ports) or EISL (TE ports). Multiple links can be combined into a PortChannel. • Increases the aggregate bandwidth on an ISL by distributing traffic among all functional links in the channel. • Load balances across multiple links and maintains optimum bandwidth utilization. Load balancing is based on the source ID, destination ID, and exchange ID (OX ID). • Provides high availability on an ISL. If one link fails, traffic previously carried on this link is switched to the remaining links. If a link goes down in a PortChannel, the upper protocol is not aware of it. To the upper protocol, the link is still there, although the bandwidth is diminished. The routing tables are not affected by link failure. PortChannels may contain up to 16 physical links and may span multiple modules for added high availability. On switches with Generation 1 switching modules, or a combination of Generation 1 and Generation 2 switching modules, you can configure a maximum of 128 PortChannels. On switches with Generation 2 switching modules only, you can configure a maximum of 265 PortChannels. A PortChannel number refers to the unique (to each switch) identifier associated with each channel group. This number ranges from of 1 to 256. OL-9285-05 Cisco MDS 9000 Family Troubleshooting Guide, Release 3.x 10-1
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