TACACS+ on ISE Deep Dive

In this post we’ll add a Network Authentication Device (NAD) to ISE to perform TACACS+ authentication and authorization. We’ll also do a deep dive on AAA commands on the NAD. First let’s start with the overall goal of the lab and an overview of how TACACS+ works.

The goal of the lab is to have two users, Bob and Alice, where Bob works in the NOC and Alice is a network admin. Based on the AD group they belong to, they should get different permissions when administrating devices. Alice will be able to use all commands, while Bob will only be able to use basic commands. This is shown below:

Why would we use TACACS+ over RADIUS? The main reason is that it gives us per command authorization and accounting. The overall flow of TACACS+ is shown below:

Enabling TACACS+

To get things started, we must first enable TACACS+ on the PSN. Go to Administration -> Deployment located under System:

Click the > symbol next to Deployment and select your PSN that you want to enable TACACS+ on:

Scroll down to the Policy Service part. Notice that Device Admin is currently not enabled:

Select Enable Device Admin Service. You Continue reading

Backup and Restore of ISE Lab Server

The ISE evaluation license gives you 90 days of full access and after that you won’t be able to make any changes. Currently, my server has 28 days remaining:

As I intend to keep labbing, I’m going to perform a backup and restore where I’ll restore the configuration on another VM that I’ll be installing. Note that this can be automated, but in this post we’re going to focus on the process of doing it manually to understand what steps are involved.

The steps that will be performed are:

  • Setup a SFTP repository to use for backups.
  • Take a configuration backup of existing node.
  • Take an operational backup of existing node.
  • Export trusted- and system certificates of existing node.
  • Install a new VM.
  • Restore the configuration from the configuration backup.

The configuration backup will give us everything we need to restore all the system settings and policies. The operational backup gives us data such as logs. While the configuration backup includes the trusted- and system certificates, it’s good to also export them separately in case you need to perform a restore using another method.

The first thing I’m going to do is to install SFTP on my Windows server using Continue reading

DO it again: how we used Durable Objects to add WebSockets support and authentication to AI Gateway

In October 2024, we talked about storing billions of logs from your AI application using AI Gateway, and how we used Cloudflare’s Developer Platform to do this. 

With AI Gateway already processing over 3 billion logs and experiencing rapid growth, the number of connections to the platform continues to increase steadily. To help developers manage this scale more effectively, we wanted to offer an alternative to implementing HTTP/2 keep-alive to maintain persistent HTTP(S) connections, thereby avoiding the overhead of repeated handshakes and TLS negotiations with each new HTTP connection to AI Gateway. We understand that implementing HTTP/2 can present challenges, particularly when many libraries and tools may not support it by default and most modern programming languages have well-established WebSocket libraries available.

With this in mind, we used Cloudflare’s Developer Platform and Durable Objects (yes, again!) to build a WebSockets API that establishes a single, persistent connection, enabling continuous communication. 

Through this API, all AI providers supported by AI Gateway can be accessed via WebSocket, allowing you to maintain a single TCP connection between your client or server application and the AI Gateway. The best part? Even if your chosen provider doesn’t support WebSockets, we handle it Continue reading

SC24 SCinet traffic

The real-time dashboard shows total network traffic at The International Conference for High Performance Computing, Networking, Storage, and Analysis (SC24) conference being held this week in Denver. The dashboard shows that 31 Petabytes of data have been transferred already and the conference has just started.

The conference network used in the demonstration, SCinet, is described as the most powerful and advanced network on Earth, connecting the SC community to the world.

In this example, the sFlow-RT real-time analytics engine receives sFlow telemetry from switches, routers, and servers in the SCinet network and creates metrics to drive the real-time charts in the dashboard. Getting Started provides a quick introduction to deploying and using sFlow-RT for real-time network-wide flow analytics.

Finally, check out the SC24 Dropped packet visibility demonstration to learn about one of newest developments in sFlow monitoring and see a live demonstration.

Cisco ISE – Admin GUI Account Locked After 45 Days

This is a quick post to describe the default behavior of the admin user GUI access in ISE, which gets locked after 45 days, if you haven’t changed the password. You’ll get something like this in the GUI:

While GUI access is prevented, you can still login via SSH and that’s how you’re going to recover the account. SSH to ISE using the admin account. Then issue the following command:

ise01/admin#application reset-passwd ise admin
Enter new password:
Confirm new password:

Password reset successfully.

If you want to change the password policy, go to Administration -> Admin Access under System and click Password Policy:

Notice the checkbox that says that the account expires after 45 days:

Uncheck this box if you don’t want to have the account expire:

Don’t forget to click Save. That’s it! That’s how you recover the account and prevent it from happening again. Note that this is for a private lab. You should adhere to any policies you have on password rotation in your organization.

Domain Joining a Windows Computer

In this post we’ll domain join a Windows 10 VM to test the GPOs that were created in a previous post. First, let’s verify that the computer is not joined to a domain:

There is currently no user certificate:

There is also no computer certificate:

To domain join the computer, we’ll go to Control Panel -> System and Security -> System and the click Advanced system settings:

Go to Computer Name and click Change…:

Select Member of Domain and enter the domain name (iselab.local in my lab):

Click OK. You’ll then be prompted for credentials with permission to join the domain:

The computer has been joined to the domain:

The computer will have to be restarted as part of joining the domain:

Select Restart Now to restart:

It will take some time…:

After logging in, certificates will be created for both the user and computer. We can verify this on the CA:

You can also use the cert manager on the client to verify the certificates. Below is the computer certificate:

The trusted root CA for computer certificates:

The user certificate:

Trusted root CA for user certs:

Before I got my setup working, I had to do Continue reading

Modifying Default User and Computer Organizational Unit In Active Directory

By default, users and computers will be placed in containers in AD. These containers don’t support the use of GPOs, which is one of the reasons to create OUs to hold the objects instead. To verify what the default user and computer container is, we’ll leverage Powershell. First, we’ll check the computers container:

PS C:\Users\Administrator> Get-ADDomain | select computerscont*                                                         
ComputersContainer
------------------
CN=Computers,DC=iselab,DC=local

Then, we’ll check the users container:

PS C:\Users\Administrator> Get-ADDomain | select userscont*

UsersContainer
--------------
CN=Users,DC=iselab,DC=local

Now, in my lab I have created iselab users and iselab computers where I want the user- and computer objects to be placed:

We’re going to user some Powershell to modify where the user- and computer objects get placed, but first we’ll get the Distinguished Name (DN) of these OUs. To do this, we’ll first have to enable Advanced Features under View:

This will display some additional containers:

Now right click the OU, such as iselab computers, and select Properties:

This will display the following window:

Now go to Attribute Editor tab, double click distinguishedName and right click and select Copy:

Then, we’ll user Powershell to redirect to this OU:

PS C:\Users\Administrator> redircmp "OU=iselab computers,DC=iselab,DC=local"
Redirection was successful.

Let’s verify what Continue reading

DNS OARC 43

The DNS Operations, Analysis, and Research Center (DNS-OARC) brings together DNS service operators, DNS software implementors, and researchers together to share concerns, information and learn together about the operation and evolution of the DNS. The most recent DNS OARC workshop was held in Prague, October 2024. Here are my thoughts on some of the material that was presented and discussed at this workshop.

NVIDIA Cumulus Linux 5.11 for AI / ML


NVIDIA Cumulus Linux 5.11 includes major upgrades to the sFlow agent that fully exposes the advanced instrumentation built into NVIDIA Spectrum-X silicon. The enhanced real-time telemetry is particularly relevant to the AI / machine learning workloads that Spectrum-X is designed to handle.

With Cumulus Linux 5.11, the sFlow agent is easily configured using nvue commands, see Monitoring System Statistics and Network Traffic with sFlow:

nv set system sflow dropmon hw
nv set system sflow collector 192.0.2.1
nv set system sflow state enabled
nv config apply

Note: In this case, enabling dropmon ensures that every dropped packet is captured, along with ingress port and drop reason (e.g. ttl_exceeded).

The same commands should be applied to every switch in the fabric for comprehensive visibility.

RDMA over Converged Ethernet (RoCE) describes how sFlow provides detailed visibility into RoCE flows used to move data between GPUs in an AI / ML data center fabric. The chart above from the RDMA network visibility demonstration at the SC22 conference shows that sFlow monitoring easily scales to the 400/800G speeds needed for machine learning.
In this example, the sFlow-RT real-time analytics engine receives sFlow telemetry from all the switches and Continue reading

AMD Now Has More Compute On The Top500 Than Nvidia

There has been a lot more churn on the November Top500 supercomputer rankings that is the talk of the SC24 conference in Atlanta this week than there was in the list that came out in June at the ISC24 conference in Hamburg, Germany back in May, and there are some interesting developments in the new machinery that is being installed. …

AMD Now Has More Compute On The Top500 Than Nvidia was written by Timothy Prickett Morgan at The Next Platform.

How We Made Fast Cloud-to-Cloud Connections Possible

The traditional way to enable things hosted in different clouds to talk to each other has been to order a physical cross-connect (a literal cable) from a colo provider that hosts the clouds’ “onramps” (private connections to the clouds’ networks) to link them. Various software-defined alternatives have emerged in recent years. Some do essentially the same thing but virtually, while others, like typical SD-WANs, rely on things like IPsec or other encryption protocols to secure connections traversing the internet. There are other, less mature approaches, including some cloud providers’ own intercloud connectivity services. And there’s always the option to send your cloud-to-cloud API requests over the public internet and hope for the best. The traditional ways tend to be costly and complex to set up, requiring specialized networking knowledge. A little more than a year ago, we decided to build a cloud-to-cloud private connectivity service that would be easier to use. The goal was to give developers who are proficient in cloud but not in networking a way to create multicloud connections and manage them with familiar tools, like Terraform or Pulumi, without hosting any infrastructure in our data centers. It was an interesting challenge, not in the least from Continue reading

SC24 Dropped packet visibility demonstration

The real-time dashboard is a joint InMon / Arista demonstration at The International Conference for High Performance Computing, Networking, Storage, and Analysis (SC24) conference being held this week in Atlanta.

Note: Click here for a live version of the dashboard during the conference, Nov 17-22.

The conference network used in the demonstration, SCinet, is described as the most powerful and advanced network on Earth, connecting the SC community to the world.

The sFlow Packet Drop Monitoring In High Performance Networks dashboard combines telemetry from all the Arista switches in the SCinet network to provide real-time network-wide view of performance. Each of the three charts demonstrate a different type of measurement in the sFlow telemetry stream:

  • Counters: Total Traffic shows total traffic calculated from interface counters streamed from all interfaces. Counters provide a useful way of accurately reporting byte, frame, error and discard counters for each network interface. In this case, the chart rolls up data from all interfaces to trend total traffic on the network.
  • Samples: Top Flows shows the top 5 largest traffic flows traversing the network. The chart is based on sFlow's random packet sampling mechanism, providing a scaleable method of determining the hosts and services responsible Continue reading

From Python to Go 003. Functions, External Modules, And Linux/MAC Environment.

Hello my friend,

We continue our journey in the realm of software development, or how some people call it programming. In the previous blog post we’ve introduced you to variables, which are the storage containers for your data. Today we’ll take a look into functions, which are next essential building of any application.

How Is Automation Important Today?

Interviewing people to various roles at high-profiles companies, I was sadly surprised that there is very low number of people who really understand network and IT infrastructure automation and are capable to write the Python code to do so. And I’m talking about companies, who are genuinely interested in good automation engineers. Don’t waste your chance, start learning network automation today:

We offer the following training programs in network automation for you:

During these trainings you will learn the following topics:

  • Success and failure strategies to build the automation tools.
  • Principles of software developments and the most useful and convenient tools.
  • Data encoding (free-text, XML, JSON, YAML, Protobuf).
  • Model-driven network automation with YANG, NETCONF, RESTCONF, GNMI.
  • Full Continue reading

HN758: How Selector Built an AI Language Model for Networking (Sponsored)

On today’s episode, artificial intelligence with sponsor Selector.AI. If you’re curious and maybe still skeptical about the value AI brings to network operations, listen to this episode. Selector is on the forefront of AIOps for networking, building models that are customized and specifically targeted at networks. What Selector is doing is NOT simply the low-hanging... Read more »

Weekend Reads 111524


Techno-futurists love to dream up visions of the future. Invariably, these are worlds where everything is under control—where every problem has a solution, and the future unfolds exactly as planned. We do seem to be moving toward some sort of centralized loss of agency.


The representational structures of the Internet governance institutions are highly varied (indicating once again that there is no “multistakeholder model”), but they all have one thing in common: decision-making power is vested in non-state actors.


The rapid expansion of AI and generative AI (GenAI) workloads could see 40% of data centers constrained by power shortages by 2027, according to Gartner.


Chiplets and 3D devices, long discussed in the future tense, are a growing sector of the market. Moore’s Law? It’s still alive, but manufacturers and designers are following it by different means than simply shrinking transistors.


Monitoring traffic at Internet Exchange Points (IXPs) is a long-standing operational practice. It is essential for several reasons related to the entire Internet infrastructure’s stability, security, and efficiency.


If you want to sell a lot of hardware to support AI workloads, then the best way to do that is to convince every country on Earth that AI is so important Continue reading

Introduction to Arista PyeAPI

Introduction to Arista PyeAPI

The Python Client for eAPI (pyeapi) is a Python library that simplifies working with Arista eAPI, removing the need to deal with the specifics of its implementation. It's straightforward to configure and use. In this blog post, we'll look at how to install pyeapi and go through some examples.

If you're familiar with Arista's eAPI, you know that you can browse to the device's IP in a browser, run commands, and get the output directly. You can also achieve the same result using Python, but it typically requires understanding which libraries to use and how to construct the REST API requests.

However, pyeapi simplifies all of this. You don't need to worry about what's happening behind the scenes. Below is a screenshot of running show vlan command via the REST API, and in the following examples, we'll see how to get the same output using pyeapi.

Introduction to Arista PyeAPI

PyeAPI Installation

To install pyeapi, you can use pip, which is the standard package manager for Python. It's a good practice to use a virtual environment (venv) to keep your dependencies isolated and avoid conflicts with other projects. First, create and activate a virtual environment. Once your virtual Continue reading

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