Head to head · 2026

Duo secures the login.
Authnull secures everything behind it.

Duo is excellent MFA for cloud apps and the perimeter. The paths that fail an audit - Active Directory, Windows logon, RDP, RADIUS, network gear, databases - sit below that line, billed per seat, one add-on at a time.

Cisco Duo
MFA you assemble by tier
VS
Authnull
Leads 11 of 15
One layer, everything included
$9/user/mo
Premier · billed per identity, every month
price
$499/mo
Flat band · same price at 100 or 500 identities
Agents you run
Windows Logon + RADIUS Proxy, self-hosted & patched
on-prem effort
Agent-optional
One policy plane, nothing extra to operate
IT + security ops
Editions, agents, and the proxy, managed by you
who runs it
Nobody dedicated
Set the policy once and move on
Cloud MFA + AD add-ons
Databases and governance sit outside entirely
scope
+ DB · IGA · TACACS+
Enforcement and governance, one flat band
Compare the costWalk it with an engineer
No forced cutoverNo rip-and-replaceCoexists with Duo
Key areas where Authnull is better

Five places a focused layer beats a per-seat platform - pick one and see the difference.

Active Directory & RDPKerberos · Windows logon
VPN & RADIUSRADIUS · 802.1X
Network gear & firewallsTACACS+ · device admin
DatabasesMySQL · PostgreSQL
Identity governancereviews · lifecycle
Needs an edition and an agent

A factor at the domain controller and every Windows RDP session - no edition to climb.

Duo's AD Defense detects attacks against Active Directory, but actually enforcing a factor at domain logon means installing the Windows Logon agent - and AD Defense itself doesn't start until the Advantage edition. Authnull challenges the domain-controller logon path directly, included by default, with local and break-glass accounts in the same policy.

Domain-controller logonRDP & interactive sessionsLocal & break-glass accountsIncluded by default
Cisco Duo
AD Defense detects attacks against AD, but enforcing a factor at domain logon needs the Windows Logon agent - and AD Defense itself starts at the Advantage edition.
Authnull
A factor challenged at the domain-controller logon path itself, included by default - local and break-glass accounts too.
Authnull vs Cisco Duo · full comparison

A complete, dimension-by-dimension comparison.

A capability-by-capability breakdown across architecture, coverage, product category, and positioning - fifteen dimensions in total, including where Duo leads.

Capability
Cisco Duo
Authnull
Core architecture
3 of 3
Approach
architecture model
Agent/app-based
Agent/app-based MFA - Duo Mobile app, Duo Auth Proxy, browser/endpoint integrations.
Credential-free
Agentless, credential-free MFA and Zero Trust access for on-prem infra.
Deployment
footprint
Auth Proxy + Duo Mobile
Requires Duo Auth Proxy for on-prem integrations (AD, RADIUS, LDAP); Duo Mobile app for push.
No endpoint agents
No endpoint agents; integrates at the protocol/directory level (AD, RADIUS, RDP, SSH, VPN).
Credential handling
standing credentials
Layered on credentials
MFA layered on top of existing credentials (password + push/OTP).
Eliminates credentials
Credential-free, session-based access - no standing credentials to steal.
Coverage
6 of 7
Active Directory
Kerberos · NTLM · LDAP
Via Auth Proxy
Yes, via Duo Auth Proxy.
Native MFA
Yes - native MFA.
RADIUS
802.1X
Well-established
Yes, well-established via Duo Auth Proxy.
Yes
Full support.
RDP
3389 · interactive
Yes
Supported.
Yes
Full support.
Linux SSH
PAM
Via Duo Unix
Yes, via Duo Unix.
Yes
Full support.
VPN
gateway access
Strongest use case
Yes - one of Duo's strongest historical use cases.
Yes
Full support.
Service accounts
NHI · machine identities
Not primary focus
Not a primary focus - Duo is largely human-user MFA.
Native support
Native support.
Cloud / SaaS apps (SSO)
SAML · OIDC
Leads
Strong - Duo integrates broadly with cloud apps and SSO, and is backed by Cisco's broader identity/security stack.
Less emphasized
Less emphasized - the product is on-prem focused.
Product category
0 of 3
Primary category
positioning
MFA + access security
MFA and access security platform, part of Cisco's identity portfolio.
Zero Trust MFA, on-prem
Zero Trust MFA for on-prem/legacy infrastructure - agentless, credential-free.
PAM
privileged access mgmt
Not core either
Not Duo's core focus either - Duo is MFA/access-first, not PAM.
Not our category
Not a category Authnull competes in for this comparison.
Risk-based / adaptive auth
device trust · policy
Leads
Yes - device trust, risk-based policies, and endpoint visibility are core features.
Not core focus
Not a stated core focus.
Positioning & target buyer
2 of 2
Core pitch
the one-line pitch
Easy MFA everywhere
“Easy-to-deploy MFA everywhere” - broad app/device ecosystem, strong brand trust via Cisco.
Agentless, credential-free
“Agentless, credential-free MFA for infra that's hard to protect” - AD, RADIUS, legacy Linux/RDP.
Best fit for
ideal buyer
Broad, mature MFA
Orgs wanting broad, mature MFA across both cloud and on-prem with minimal friction, backed by an established vendor.
Heavy legacy/on-prem footprint
Orgs with a heavy legacy/on-prem footprint wanting agentless, credential-free coverage.

Authnull leads on 11 of 15 dimensions and ties on 2. The remaining 2 - cloud/SaaS SSO and risk-based/adaptive auth - are areas where Duo leads.

Get this as a scorecard
Pricing worksheet

Do the math with your own numbers.

Duo bills per seat, so the cost climbs with every identity you add - and the on-prem coverage you're here for lives in its higher editions. Authnull is a flat price per band: the same bill at 100 identities or 500, every protocol and governance included. Set your headcount and the Duo edition that covers your gap.

Sticker priceAuthnullCisco Duo
Entry tierStandard - $499/mo flat (up to 500 identities)Free - $0/user/mo (≤10 users only)
Mid tierGrowth - $900/mo flat (up to 1,000 identities)Essentials - $3/user/mo
Advanced tier—Advantage - $6/user/mo ("Most Popular")
Top tierEnterprise - Custom (1,000+ identities)Premier - $9/user/mo
Pricing modelFlat-rate band - same price whether you have 50 or 500 usersPer-user - cost scales linearly with headcount
Being upfront: below roughly 80 identities, Duo's per-seat pricing - or its free tier for 10 users or fewer - can undercut Authnull's flat $499/mo floor. The math below favors Authnull at higher headcounts; drag the slider down to see where that crosses for your own team.
Identities250
Duo edition to compare

Advantage adds AD Defense and risk-based auth. VPN-less remote access still requires Premier, and you still install and run the Windows Logon agent and the RADIUS Authentication Proxy yourself - across every user, at this per-user rate.

Line itemCisco Duo · AdvantageAuthnull · Standard
Billing model$6/user/mo × every identityFlat band · ≤ 500 identities
Monthly total$1,500/mo$499/mo
Annual total
at 250 identities
$18,000 /yr$5,988 /yr
On-prem components you operateWindows Logon agent + RADIUS Auth Proxy - self-hosted & patchedSelf-hosted in your environment, agent-optional
AD · RDP · RADIUS · firewalls Add-ons, higher editions Included
Databases (MySQL · PostgreSQL) Not offered Included
Identity governance (IGA) Not offered Included
$12,012/yr less than Duo Advantage - one flat band, everything included.

Duo figures use publicly published list prices ($3 / $6 / $9 per user / month, Essentials / Advantage / Premier) and don't include the Authentication Proxy and Windows Logon components you self-host and maintain. Authnull bands ($499/mo Standard ≤ 500, $900/mo Growth ≤ 1,000, custom above) include every protocol, factor, and governance. Confirm everything against your quote - this worksheet is for scoping, not a contract.

How teams switch

Coexist, consolidate, replace - at your pace. No forced cutover.

01 / start here
Coexist

Keep Duo exactly as-is on cloud apps. Drop Authnull onto the unprotected paths - AD logon, RDP, RADIUS, firewalls, databases - with governance over all of them. Nothing you rely on changes.

No disruption to users
Closes the audit finding in days
02 / save on ops
Consolidate

Move overlapping paths - RDP, VPN - onto one policy plane. Retire the Duo components you were self-hosting and drop down a Duo edition you no longer need.

Fewer components to operate
One log stream, one policy model
03 / your call
Replace (optional)

When you're ready, Authnull co-exists on cloud SSO too - so you can retire Duo entirely, or keep it for the device-trust features you like. Your call, not a forced cutover.

No deadline imposed by us
Keep what works for you

Bring your Duo setup. We'll show you exactly what's still uncovered.

Twenty minutes, your real environment, no slides - we'll show you which flagged paths we close today, and be honest about the ones we don't.

Book a comparison call