Runbook of the Week: Layer-2 Architecture Assessment

Matthew Speidel
By Matthew Speidel March 10, 2017 4 minute read
Matt is NetBrain's Technical Training Engineer, the first stop for all how-to questions about the NetBrain platform. He's been with NetBrain since 2015. When he's not answering technical questions or making tutorial videos, Matt enjoys reading, writing, and playing video games. He is also an avid historical reenactor.

Hi again! If you recall, in my last article I discussed how NetBrain’s Runbook automation speeds up the process of assessing and troubleshooting a network’s routing topology. (It also saves you aspirin!)

This week, let’s suppose you need to understand the state of your network’s Layer-2 architecture in order to troubleshoot a problem.

Flow of a NetBrain Runbook for routing design assessment

With NetBrain, you can use a Runbook to perform this L2 assessment quickly and easily. Let’s take a look together at how this can be efficiently accomplished with a Runbook.

Step 1: Highlight VLANs

In this example, the first step is to figure out which VLAN is configured on each switch port. This is easily done by running a Qapp, which visually highlights switch ports according to their configured VLANs. We humans are very visual creatures, so data that’s displayed graphically is much easier and quicker to comprehend.

Remember: Each Runbook step is executable. You need only click the “Play” button and select “Run.” The Qapp (or whichever action is configured on the Runbook step) then executes, and results are displayed right on the Qmap for analysis.

In the example above, you can see at a glance that most of the access-mode ports on the map pictured above are configured for VLAN 1. However, the access mode port highlighted in orange is configured for VLAN 10.

Step 2: Check STP Status

The next step in this Runbook is to check the spanning-tree status of your key VLANs. In this case, you’d focus on VLAN 1 first and foremost. All you need to do is select the VLAN you desire, click “Highlight,” and simply let the Qapp do its thing.

Check out the screenshot above. As you see, the Qapp shows both the blocked ports and the allowed ports for VLAN 1.

It even points out the root bridge. How cool is that?


Step 3: Check STP Design

This Runbook then guides you to the next logical procedure: checking each device’s STP configuration. Again, upon running the Qapp and selecting VLAN 1, the Qapp pulls all relevant data from each device via CLI. In this case, the data is filtered and popped onto the map as a helpful sticky note linked to each device.

Perusing the sticky notes, you can swiftly see three devices are configured for RPVST, while the other three switches are configured for MST. This should be remedied ASAP!


Step 4: Collect STP Show Commands

The next Runbook step is to pull a range of raw STP data, which will allow you to drill down and check specifics. To do this, you simply click the “Play” button for the next executable (“Collect STP CLI”), then select “View Output” to see the data. Finally, you sort by device and command, and again, this data is then embedded in the Runbook for recall at will.


Step 5: Monitor General Health

It’s always a good idea to cap off any network assessment by running the Overall Health Monitor, a built-in Qapp that checks CPU, memory, and bandwidth utilization via SNMP.

In the screen capture above, you can see that the Qapp reveals that a couple ports on each switch are either down or administratively down.

Step 6: Monitor Interface Errors

Finally, it’s always wise to check if any switch ports are reporting I/O errors. Run this final Qapp via the “Play” button, and the Qapp pulls a show int command on each device, noting the basic error stats beside each interface. Any value above 0 will be noted in orange, while any value that has delta will be noted in red. Everything’s green in the screenshot below, so we know everything’s okay in that respect. 

Remember, all the data you pulled as part of the L2 assessment is now integrated within the Runbook, which in turn is embedded directly within the QMap file. Also, bear in mind Runbooks are easy to build and fully customizable.

So, that’s my quick overview of Layer-2 architecture assessment in NetBrain. If you want to watch a short video of me walking through this Runbook, click here.