[Day 14] Cisco ISE Mastery Training: Setting Up a Test Switch for Authentication

• Trainer Sagar Dhawan
• Posted on August 18, 2025
• No Comments

[Day 14] Cisco ISE Mastery Training: Setting Up a Test Switch for Authentication

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Introduction

In Cisco ISE deployments, a Test Switch is your lab’s workhorse. Before rolling NAC (802.1X/MAB) into production, you need a safe environment to test authentication policies, VLAN assignments, and posture checks.
This session walks you through configuring a switch from scratch to talk to ISE, authenticate endpoints, and provide live validation using both CLI commands and ISE GUI logs.

A properly configured test switch is critical for:

• Verifying policy behavior before production rollout
• Avoiding downtime on live networks
• Learning ISE workflows hands-on

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Problem Statement

Deploying ISE without pre-testing device configurations can lead to:

• Authentication loops or endpoint lockouts
• VLAN misassignments and network outages
• Misconfigured RADIUS settings that fail silently

Without a dedicated test switch, you risk learning the hard way — directly on production gear.

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Solution Overview

Cisco ISE allows you to register a test switch as a network device, apply RADIUS policies, and monitor endpoint authentications in a controlled setup. By integrating a switch in lab mode, you can:

• Validate 802.1X and MAB
• Confirm dynamic VLAN assignments
• Troubleshoot authentication issues before they impact users

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Sample Lab Topology

Text Description:

• VMware/EVE-NG running Cisco ISE (2.7+ recommended)
• 1x Cisco Catalyst Switch (EVE-NG virtual or physical)
• 1x Test Endpoint (Laptop/VM with supplicant enabled)
• Optional: AD server for external authentication
• Management PC with SSH/HTTPS access to switch and ISE GUI

Traffic Flow:
Test endpoint → Switch Access Port → RADIUS request to ISE → Policy check → VLAN assignment → Access granted/denied

Diagram Description:

• ISE authenticates/authorizes the admin (optionally via AD), applies roles/command sets, and logs accounting for every admin action
• Admin PCs SSH to the Test Switch (or WLC) to perform device administration.
• The Switch/WLC forwards TACACS+ (TCP/49) and RADIUS (UDP/1812/1813) requests to Cisco ISE.

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Step-by-Step GUI & CLI Configuration Guide

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Step A – Add Switch to ISE (GUI)

1. Log into ISE GUI.
2. Navigate: Administration → Network Resources → Network Devices
3. Click Add.
4. Fill details:
   • Name: TestSwitch01
   • IP Address: 192.168.10.2
   • Device Type: Switch
5. Enable RADIUS Authentication Settings.
6. Enter Shared Secret (match CLI config).
7. Click Submit.
   [Screenshot: ISE Network Device Add Screen]

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Step B – Configure Switch for ISE Integration (CLI)

conf t
! Enable AAA
aaa new-model

! Define RADIUS server
radius server ISE1
 address ipv4 192.168.10.10 auth-port 1812 acct-port 1813
 key MySharedSecret

! AAA Authentication & Authorization
aaa authentication dot1x default group radius
aaa authorization network default group radius
aaa accounting update periodic 5
aaa accounting dot1x default start-stop group radius

! Enable 802.1X globally
dot1x system-auth-control

! Configure an access interface
interface FastEthernet0/1
 switchport mode access
 authentication port-control auto
 mab
 dot1x pae authenticator
 spanning-tree portfast

! Set RADIUS as source interface
ip radius source-interface vlan 10
end

! Save config
write memory

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Step C – Enable Endpoint Supplicant (Windows example)

1. Go to Control Panel → Network and Sharing Center.
2. Click active Ethernet → Properties.
3. Enable 802.1X under Authentication tab.
4. Choose PEAP and validate certificate if using EAP-TLS.

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Step D – Create ISE Policy Set for Test Switch

1. Policy → Policy Sets → Add
2. Name: Lab_Switch_Auth_Test
3. Condition: Device Type = Switch AND IP = 192.168.10.2
4. Authentication Policy:
   • 802.1X: Use Internal Users or AD
   • MAB: Internal Endpoints
5. Authorization Policy:
   • 802.1X: VLAN 20
   • MAB: VLAN 30 (Guest)
     [Screenshot: ISE Policy Set Screen]

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Step E – Validation

From Switch CLI:

show authentication sessions interface Fa0/1
show aaa servers
debug radius authentication

From ISE GUI:

• Go to Operations → RADIUS → Live Logs.
• Check for green checkmarks for success and VLAN assignment details.

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FAQs

Q1: Do I need a physical switch or can I use EVE-NG for this lab?
A: You can use either. Physical Catalyst switches give you realistic port-level behavior, but EVE-NG with virtual IOS (IOU or vIOS) works fine for learning the AAA/RADIUS flow. Just ensure the virtual switch image supports 802.1X and MAB commands.

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Q2: Which VLAN should I configure on the test switch?
A: Configure an access VLAN for authenticated devices (e.g., VLAN 20) and optionally a guest VLAN (e.g., VLAN 30) for unauthenticated/MAB endpoints. These VLANs should exist on the switch and be routable to ISE.

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Q3: What’s the difference between MAB and 802.1X in testing?
A:

• 802.1X: Requires a supplicant (like Windows, macOS, or AnyConnect NAM).
• MAB: Uses MAC address as the credential when no supplicant is present.
  When testing, it’s best to configure both so you can simulate different endpoint scenarios.

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Q4: My authentication keeps failing — what’s the first thing I should check?
A:

1. Verify the shared secret matches between ISE and the switch.
2. Check RADIUS reachability using show aaa servers.
3. Look at ISE Live Logs for the failure reason — usually, it’s wrong credentials or missing policy match.

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Q5: How do I clear a stuck authentication session on the switch?
A: Use:

clear authentication sessions interface Fa0/1

This forces the port to restart the authentication process.

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Q6: Can I run 802.1X without enabling it globally?
A: No — dot1x system-auth-control must be enabled globally before any interface can participate in 802.1X authentication.

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Q7: What’s the difference between RADIUS Authentication and Authorization?
A:

• Authentication: Verifies the user/device identity (e.g., username/password or MAC).
• Authorization: Decides what access to grant (e.g., VLAN, ACLs, downloadable ACLs) after authentication.

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Q8: Can I test downloadable ACLs (dACL) in a lab switch?
A: Yes, as long as the switch IOS supports dACLs. You’ll configure them in the ISE Authorization Profile and see them pushed to the switch during authentication.

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Q9: How can I monitor real-time authentication attempts from the switch side?
A: Use:

debug radius authentication
show authentication sessions

And watch ISE’s Operations → RADIUS → Live Logs at the same time to correlate results.

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Q10: What’s the minimum configuration I need on the switch for a quick test?
A:

aaa new-model
radius server ISE
 address ipv4 <ISE-IP> auth-port 1812 acct-port 1813
 key <secret>
aaa authentication dot1x default group radius
dot1x system-auth-control
interface Fa0/1
 switchport mode access
 authentication port-control auto
 mab
 dot1x pae authenticator

That’s enough to get basic MAB and 802.1X working for lab validation.

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YouTube Link

For more in-depth Cisco ISE Mastery Training, subscribe to my YouTube channel Network Journey and join my instructor-led classes for hands-on, real-world ISE experience

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Closing Notes

A test switch is your ISE proving ground. Mastering switch-side 802.1X/MAB configuration and ISE policy mapping here ensures a smooth, outage-free deployment later. Validate every change via CLI and ISE Live Logs for confidence before production rollout.

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