Hands-on with Arista VM Tracer

Starting November 7th, 2016, HPE announced that they were partnering with Arista Networks for all datacenter networking opportunities moving forward. Arista’s been making a lot of waves in the industry recently, so as strategic HPE partners, we are very excited about the technology that Arista brings.

Arista’s networking portfolio uses Fedora Linux at the core. Useful tools like grep, cat, zcat, tcpdump, awk and more are ready to go from boot. Administrators can choose to work in the bash shell if they are familiar with Linux or work in the more conventional Arista CLI. Because of the Linux architecture, common networking protocols like STP, OSPF, BGP all run as individual processes and can be isolated if problems pop up. VXLAN, MLAG and other datacenter focused technologies are supported as well.


Arista VM Tracer and Existing vCenter

One unique tool that stood out to me during our week long technical deep dive was the Arista VM Tracer technology. VM Tracer allows the Arista switch to keep an eye on the virtual environment by collaborating with an existing vCenter server. Recently we published a post around NSX and how it marries the physical network infrastructure with the virtual, solving a lot of problems for the large datacenter and the inherent scaling issues present there. Note that Arista does fully support the VXLAN tunnel overlay I described (in fact Arista was one of the co-authors of the VXLAN standard), but the Arista gear also presents a new convenient solution and quality of life enhancement for smaller datacenters that still utilize an L2 topology with Arista’s VM Tracer tech.

Arista VM Tracer Walkthrough

It’s always better to show than tell, so here’s a quick walkthrough of how VM Tracer “ticks” underneath the hood.

First, within the CLI of the Arista switch, we configure VM Tracer to communicate with vCenter – see below:

Once this is up and running, the Arista switch and the VMware environment can start exchanging information and collaborating. Running the command, show vmtracer sess, brings up the session information and lets us know that we’re all set.

After a few minutes, Arista’s database of virtual machines will populate. You can check the database with show vmtracer vm, which lists out the VMs, their host, and where they connect to the Arista switch. In this example, everything is connecting via the trunk port Et1.

We can pull more information on each VM with the “detail” flag.

Pull From Multiple Sources with XMMP

Someone who is already proficient with Linux will be able to use pipes and all their familiar data scraping commands to quickly filter through this information across their datacenter. Arista also supports XMMP for multi-switch CLI, so you can pull info from multiple sources simultaneously through pre-defined XMMP switch groups. Below is a sample where I request information on a specific VM – note that you can very quickly determine where a VM is connected using this tool.

Dynamically Add VLANS

VM Tracer includes another useful function called “autovlan” that is enabled by default. You can verify whether it’s working by pulling up the VM Tracer session as shown below. If a vmotion action moves a VM from one host to another, the physical network infrastructure tied to the new host must support the same VLANs that were present on the original switch. This can lead to frustration as network administrators must constantly add and re-add VLANs manually to each switch port as the VMs bounce around the VMware environment. The VM team winds up waiting on the network team to configure the switch VLANs manually, and the network team gets loaded up with busywork. But by using VM Tracer technology, the Arista switch can dynamically add VLANs to switches to support VMs as they move around the datacenter.

Here I run a sho VLAN command to see what is active on my switch. Notice that VLANs tagged with an asterisk have been added to the switch dynamically with autovlan. No manual administrative intervention was required.

Cool, huh?

Control of Autovlan in VM Tracer

Don’t worry, you can reign in the autovlan function as needed. Let’s say I want to ensure that VLAN 1001 does not automatically populate on my switch for some security reason. I can go back into the Lab VM Tracer session and remove 1001 from the allowed-vlan pool:

To confirm that change, run sho vmtracer sess.

Now I can pull up the list of VLANs again and confirm that VLAN 1001 is no more.

I hope you’ve found this quick walkthrough of VM Tracer useful. There are many innovative features available on the Arista lineup as well (for example, pulling information via chat programs) but I’m already starting to push the acceptable length guidelines for a single blog post. Needless to say, we’re excited to partner with the Arista team. If you’d like to learn more about the latest trends in datacenter networking, please contact the Edge team online of call us at 888-861-8884.

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