Tag Archives: Cisco Nexus 5596UP

Choosing between Dynamic and Static FEX interfaces pinning

Cisco Nexus 2200 Fabric Extenders can be connected to the parent switches using two different modes: Static and Dynamic interfaces pinning. Static pinning mode instructs the switch to virtually split FEX into few blocks of ports and statically associate each block of ports with its own physical uplink. In other words, if one particular uplink fails, a range of FEX ports, associated with this uplink, fail as well. Hence, the word Static. Dynamic pinning mode is based on a Port-Channel logic. In very basic scenario you would have all your physical uplinks associated with a single Port-Channel that will stay up as long as there is at least one working physical uplink. At first glance, difference seems to be obvious and not in the favor of Static mode. But let’s dive into the subject to understand when Static mode becomes handy. Read more …

Configuring Cisco Nexus 5500 series switches with Dual-Homed FEXes

More and more Enterprises come to a decision to deploy Cisco Nexus switches in their corporate data centers. One of the main design considerations relates to Cisco 2200 Fabric Extenders (FEX) connectivity topology. To provide high availability Cisco Nexus 5500 series switches support different options to connect FEXes (all are based on a Virtual Port Channel feature):

  • Straight-Through, where every FEX is connected to a single N5K (Active/Active and Active/Passive servers);
  • Dual-Homed, where each FEX has one or more uplinks to two N5K switches (Active/Passive servers);
  • Enhanced vPC, same as Dual-Homed but with Active/Active servers;

Each option has its own limitations and field of use, but this time we will concentrate our attention on the Dual-Homed FEX topology with Active/Standby Dual-Homed servers. Mainly because I recently deployed a pair of Cisco Nexus 5596UP switches with a number of Cisco 2248 TP-E Fabric Extenders using this approach.

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FET-10G considerations

We are currently deploying new data centers using brand new Cisco Nexus 5596UP switches with Fabric Extenders (Cisco Nexus 2248TP-E). When you order a bundle from Cisco (switches and FEXes) it goes pre-packed with FET-10G modules (8 per FEX). Ok, not pre-packed, you actually need to include those modules into the order for free. The reason I am making notes on this is due to the additional configuration required for this module to be discovered. If you simply put it into the switch, it will show those modules as Invalidated. For them to work, it is required to manually change switchport mode to “fex-fabric” – switchport mode fex-fabric. Once you’ve done that, FET-10G will be recognized and any FEX behind it will be discovered.

This can be confusing if you’re deploying Nexus switches and FEXes using this modules for the first time. They have a limited scope of use – only switch to FEX connections. They go for free when you buy bundles, so make sure to include them into your order! You won’t be able to get them for free later (or even buy them). General SFP+ modules will discover any connected FEXes automatically.