The Cisco Nexus switches allow a very high level of bandwidth connectivity positioned as data center switches. The Nexus switches do not support the same features and flexibility as local area network (LAN) based switches, but provide the very high capacity and cost effectiveness needed in data center environments. Nexus switches run a new operating system called Cisco NX-OS and provide various Ethernet based interface speeds varying from 100Mbps to 10Gbps depending on the Nexus platform. The Cisco Nexus product line currently consists of the following product families:
- Nexus 1000
- Nexus 2000
- Nexus 5000
- Nexus 7000
All Nexus platforms run the Cisco NX-OS operating system that is very familiar to Cisco IOS, but offers much more flexibility and reliability than Cisco IOS. The Nexus 1000 supports many virtualization technologies that are in VMWare ESX platforms and VMWare’s newer vSphere technologies. The Nexus 2000 and 5000 platforms provide layer 2 connectivity, while the Nexus 7000 provides layer 3 connectivity.
This blog will focus on a deployment model leveraging the Nexus 5020 and Nexus 2148 devices. The Nexus 5000 platforms provide non-blocking backplane architectures with onboard capacity of twenty (5010) or forty (5020) 10 Gigabit Ethernet interfaces with one to two expansion slots respectively. The expansion modules have the ability to provide additional 10 Gigabit interfaces and fiber channel over Ethernet (FCoE) connectivity. The first 8 port (5010) or 16 (5020) ports of the 5000 platform can be configured to provide 1 Gbps connectivity using small form-factor pluggable (SFP) optics, while all the ports can provide 10 Gbps connectivity over SFP+ optical interfaces. The Nexus 5000 platforms support connectivity to the Nexus 2148 through a fabric extender (fex) configuration as of NX-OS 4.0(1a).
The Nexus 2148 platform does not have a local console port or any way to directly configure the device. The Nexus 2148 data center switch is managed through the Nexus 5000 configuration. The Nexus 2148 appears as a line card in the configuration of the Nexus 5000 after the fabric extender interface is properly configured and comes online. The Nexus 2148 downloads NX-OS software from the Nexus 5000. After the 2148 is online, 48 new configurable interfaces appear in the Nexus 5000 configuration.
The Nexus 2148 platform provides 48 Gigabit Ethernet interfaces and up to four fabric extender (fex) interfaces to the Nexus 5000 platforms. The Nexus 2148 supports up to four 10 Gigabit Ethernet (GE) fabric extender interfaces to the Nexus 5000 platform, but the Nexus 2148 can only uplink to one Nexus 5000 with NX-OS 4.0(1a). NX-OS 4.1(3) supports redundant uplink connections to two different Nexus 5000 switches providing interface and path redundancy.
IEEE 802.1d Spanning Tree Protocol (STP) is enabled on the Nexus 5000 by default and all redundant paths between the Nexus 2000 and 5000 are placed in the blocking state by STP. Two channel groups can be configured to each Nexus 5000 which will result in two forwarding (channel group 1) and two blocking interfaces (channel group 2) which still results in sub-optimal bandwidth utilization. See comments below for correction.
Virtual port channel (vPC) technology introduced with Nexus 5000 NX-OS 4.1(3) allows the 2148 platform to use all four interfaces uplinked to the Nexus 5000. vPC technology is similar to the virtual switching system (VSS) technology introduced in the Catalyst 6500 VSS supervisor module which is similar in nature to multi-chassis Etherchannel (MCEC). All the above technologies allow the uplink switch to appear as one virtual switch to the downstream devices. Loop avoidance is provided through a vpc link interface between the Nexus 5000 switches which requires a special configuration. Path recalculation is performed in under one second on the Nexus platforms in the event of a link or device failure.
Data Center Switches
Special thanks to Guest Author Dennis Hartmann for this post.