Network Assessment Methodology

Terry Slattery
Principal Architect

At NetCraftsmen, we’ve been doing network assessments and network designs on a regular basis for some pretty large customers. NetMRI has become a strategic component of our assessment process.

While there are multiple facets to a good assessment, I’m going to focus this article on understanding the customer’s existing network. There are numerous problems with manual methods to do network discovery and network assessment. They involve human error, take a long time, and require a smart network engineer to perform a lot of repetitive tasks (increasing the possibility of human error). As the network increases in size, the task becomes increasingly difficult.  It becomes nearly impossible for the network engineer to provide significant value in the assessment when much of the time is spent collecting basic information.

NetMRI automates the process of network discovery, data collection, and analysis of the collected data, allowing us to focus on the assessment and providing value to our customers. We set it up, get it started, and perform other tasks while it discovers network devices, archives configurations, and collects operational data. After 2-3 days of data collection, NetMRI will have enough data for us to perform an assessment (we often let it run for a week so that we have a week of operational data). We then examine the following data:

  • Physical
    • Inventory of devices and identify those that are End-of-Life or End-of-Sale
    • OS versions and whether there are multiple versions per hardware platform
    • Environmental data such as power supplies, fans, temperature
    • Interfaces in up/down state (router interfaces and switch trunking interfaces)
    • Duplex mismatch, and ports running at 100/Half, which is an unusual configuration
    • Interface errors and discards
    • Interfaces with high utilization
  • Layer 2 (Switching)
    • Large VLANS (STP domains) spanning many switches – vulnerable to STP loops
    • Number of VLANs and their naming and numbering
    • Root bridge selection in each VLAN
    • STP loop protection mechanisms – BPDUGuard, LoopGuard, RootGuard, etc
  • Layer 3 (Routing)
    • Identify routing domains, indicating routing complexity
    • Routing protocols in use and which devices are running them
    • Routers that are originating default routes, which are possible black holes
    • HSRP/VRRP/GLBP routers with no peer router, compromising redundancy
    • Subnets with no edge devices or subnets that are nearly full
    • IP addressing
  • Configurations
    • Basic service consistency (syslog, snmp, AAA, NTP)
    • QoS configuration consistency
    • Running configs that are not saved
    • Repository to grep for various things

We use the data to learn how consistently the network has been maintained, what types of latent problems exist, whether it follows best practice designs, and where it can be improved. Consistency of operations tells how well the network is run. Large VLANs without STP loop protection mechanisms in place tells us that current design practices are not in use.

NetMRI allows us to focus our efforts on helping the customer understand risks of the current network design and how operations can be improved. The result of a network assessment for the customer is that they can improve their network, starting with the greatest risk items. As the network design and operations improves, there is less downtime, which translates into greater business productivity – and that’s what helps our customers be more productive.



Re-posted with Permission 

NetCraftsmen would like to acknowledge Infoblox for their permission to re-post this article which originally appeared in the Applied Infrastructure blog under


Leave a Reply


Nick Kelly

Cybersecurity Engineer, Cisco

Nick has over 20 years of experience in Security Operations and Security Sales. He is an avid student of cybersecurity and regularly engages with the Infosec community at events like BSides, RVASec, Derbycon and more. The son of an FBI forensics director, Nick holds a B.S. in Criminal Justice and is one of Cisco’s Fire Jumper Elite members. When he’s not working, he writes cyberpunk and punches aliens on his Playstation.


Virgilio “BONG” dela Cruz Jr.

CCDP, CCNA V, CCNP, Cisco IPS Express Security for AM/EE
Field Solutions Architect, Tech Data

Virgilio “Bong” has sixteen years of professional experience in IT industry from academe, technical and customer support, pre-sales, post sales, project management, training and enablement. He has worked in Cisco Technical Assistance Center (TAC) as a member of the WAN and LAN Switching team. Bong now works for Tech Data as the Field Solutions Architect with a focus on Cisco Security and holds a few Cisco certifications including Fire Jumper Elite.


John Cavanaugh

CCIE #1066, CCDE #20070002, CCAr
Chief Technology Officer, Practice Lead Security Services, NetCraftsmen

John is our CTO and the practice lead for a talented team of consultants focused on designing and delivering scalable and secure infrastructure solutions to customers across multiple industry verticals and technologies. Previously he has held several positions including Executive Director/Chief Architect for Global Network Services at JPMorgan Chase. In that capacity, he led a team managing network architecture and services.  Prior to his role at JPMorgan Chase, John was a Distinguished Engineer at Cisco working across a number of verticals including Higher Education, Finance, Retail, Government, and Health Care.

He is an expert in working with groups to identify business needs, and align technology strategies to enable business strategies, building in agility and scalability to allow for future changes. John is experienced in the architecture and design of highly available, secure, network infrastructure and data centers, and has worked on projects worldwide. He has worked in both the business and regulatory environments for the design and deployment of complex IT infrastructures.