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Cisco · ISE 3.3 · Lesson 11 of 12

ISE vs Forescout vs ClearPass: same job, different first move

Interview: “We have Forescout, why ISE?” If you say “ISE is better” you lose. If you translate — RADIUS 802.1X vs agentless visibility — you sound hireable.

Updated 2026-08-18·16 min read·L2 primary·Quiz at end

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The ticket

You trained ISE. The shop bought Forescout for OT. They still need 802.1X for laptops. Both can live together via eyeExtend / pxGrid — if you know who owns which decision.

Quick interview answer

ISE is RADIUS-first: 802.1X, MAB, CWA, dACL. Forescout is visibility-first: discover and classify without a supplicant, then enforce (virtual firewall, switch plugin, or hand off to ISE). ClearPass is Aruba’s RADIUS NAC cousin. Many campuses: Forescout sees everything; ISE authenticates users.

Hero · three boxes
Three NAC approaches side by side
OT cameras rarely speak PEAP. Laptops should not rely on MAB forever.
Lab data · dummy only

PAN ise-pan 10.10.10.20 · PSN ise-psn1 10.10.10.21 · MnT ise-mnt 10.10.10.22 · NAD sw-access-01 10.10.10.2 · AD dc01 10.20.30.10 · Priya 10.20.30.80 TECHCLICK\priya.hr · printer 10.20.30.60. Not a live customer.

Translation table

IdeaISEForescoutClearPass
BrainPAN / PSNEnterprise Manager / AppliancePublisher / Subscriber
User auth802.1X PEAP/EAP-TLSOften via ISE/NPS plugin802.1X
Agentless deviceMAB + profilingeyeSight discoveryProfiling
EnforcedACL / VLAN / CoAVirtual FW / switch plugin / ISEEnforcement profiles
LogsLive LogsPolicy / host logAccess tracker

When each bites

NeedLead with
User identity on campus portsISE 802.1X
OT / IoT / medical with no supplicantForescout visibility, careful enforce
Aruba wireless estateClearPass is native; ISE still works
Both users and OTForescout + ISE together

Interview answer

  1. Their word

    “eyeSight is your discover. On ISE I would call that profiling + Context Visibility.”

  2. One proof

    ISE: Live Logs. Forescout: host profile + policy hit.

  3. One failure

    Unknown permit-all, or 802.1X on a PLC.

Four mix-ups

1 · Calling Enterprise Manager “the PSN”

2 · 802.1X on OT because “NAC requires it”

3 · Two systems enforcing opposite VLANs

4 · Brand rant

Say it out loud

30-second version

ISE authenticates users with RADIUS and downloads dACLs. Forescout finds devices that cannot authenticate and can orchestrate ISE or the switch. I would not run two conflicting enforcement owners on the same port.

Traps

They sayYou say
Agentless NACForescout visibility or ISE MAB+profile
Policy setForescout policy tree / ClearPass service
CoASame idea: bounce the session after classify

Knowledge check

Judgment items. One best answer. Reasons send you back to the matching section.

Q1

ISE’s first superpower vs Forescout?

Correct: a. Quick answer.
Q2

Forescout’s first superpower vs ISE?

Correct: a. Concept.
Q3

OT PLC with no supplicant. Worst first move?

Correct: a. Mix-up 2.
Q4

Two NACs on one port. Risk?

Correct: a. Mix-up 3.
Q5

ClearPass is closest to…

Correct: a. Table.
Q6

Best interview move?

Correct: a. Runbook.

Cisco ISE class series: Personas · First day · NAD + RADIUS · Policy sets · Wired 802.1X · MAB · CWA / guest · Profiling · dACL vs VLAN · Live logs · vs Forescout · Interview

Sources

Related: ISE evidence desk · session factory · Forescout series.